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K E Carlson

Publications and source records attributed to K E Carlson.

At least 37 records · Page 2Linked to original sources
PubMed1994

Oxohexestrol derivatives labeled with fluorine-18. Synthesis, receptor binding and in vivo distribution of two non-steroidal estrogens as potential breast tumor imaging agents.

We have prepared two non-steroidal estrogens in the 2-oxohexestrol series labeled with the positron-emitting radionuclide fluorine-18, 1-fluoro-5-oxohexestrol (4) and 1-fluoro-2-oxohexesterol (5). We anticipated that the polar ketone function at the interior of these ligands would reduce their level of non-specific binding, which might increase the selectivity of their uptake in vivo. The two compounds were prepared by total synthesis: compound 4 was prepared in fluorine-18 labeled form by [18F]fluorine ion displacement on a suitably protected methanesulfonate precursor followed by deprotection under acidic hydrogenolytic conditions; the isomer 5 was prepared from a protected alpha-keto trifluoromethanesulfonate precursor with deprotection under basic conditions as the final step. The binding affinity of these hexestrol derivatives for the estrogen receptor was determined by competitive radiometric binding assays at 0 and 25 degrees C, and their lipophilicity (as octanol-water partition coefficients, log P values) and non-specific binding were estimated. The log P values determined by a reversed phase HPLC method were higher, relative to estradiol, than those calculated by the fragment method of Rekker. In tissue distribution studies in immature (50 g) rats, both of these compounds showed selective uptake in estrogen target tissues. At 1 h, activity in the uterus reached the level of 2.5-3.0% of the injected dose per gram tissue, with uterus-to-blood and uterus-to-muscle ratios of 14-20 and 8-14, respectively. The uptake efficiency and selectivity of these fluoro-oxohexestrols in principal estrogen target tissues is less than that of fluorine-18 labeled steroidal estrogens we have prepared previously, but their receptor-mediated uptake in certain secondary target tissues is substantial. The specific and non-specific components of target tissue uptake of these two compounds appear to be directly related to their non-specific binding and their binding selectivity.

Animals↗
PubMed1993

16 beta-([18F]fluoro)estrogens: systematic investigation of a new series of fluorine-18-labeled estrogens as potential imaging agents for estrogen-receptor-positive breast tumors.

In order to understand the structural features that might lead to an estrogen receptor (ER) based breast tumor imaging agent with improved uptake characteristics, we have synthesized several new analogs of 16 beta-fluoroestradiol (beta FES) and studied their tissue distribution in immature rats. The compounds we prepared were 11 beta-methoxy-beta FES (7a), 11 beta-ethyl-beta FES (7b), 17 alpha-ethynyl-beta FES (8c), 17 alpha-ethynyl-11 beta-methoxy-beta FES (8a), and 11 beta-ethyl-17 alpha-ethynyl-beta FES (8b). All of the analogs exhibit good affinity for ER, ranging at 25 degrees C from 10 to 460, with estradiol equal to 100. Measurement of their octanol/water partition coefficients by an HPLC method allowed us to estimate their level of nonspecific binding and thereby to predict their binding selectivity indices (BSI, i.e., the ratio of their ER-specific to nonspecific binding); the BSI values of three fluorine-substituted analogs exceed that of estradiol. These ligands have been labeled in the 16 beta position with fluorine-18 by the nucleophilic displacement of an alpha-disposed trifluoromethanesulfonate by [18F]fluoride ion. Reduction with lithium aluminum hydride produced the estradiol series ([18F]-7a-c), while treatment with lithium trimethylsilylacetylide afforded the ethynylated series ([18F]-8a-c). The synthesis time was 85 min for [18F]-7a-c and 120 min for [18F]-8a-c, with radiochemical yields ranging from 16 to 43%, and effective specific activities being 90-2900 Ci/mmol (3.3-107 TBq/mmol). In tissue distribution studies in immature female rats, all of the labeled analogs demonstrated ER-selective uptake in the principal target tissues, the uterus and the ovaries, and also in organs with lower titers of ER, the secondary target sites kidney, thymus, fat, and muscle. Although factors other than specific and nonspecific binding obviously affect the tissue distribution of these 16 beta-fluoroestrogens, we find that their ER-specific uptake by both the principal and the secondary target tissues correlates with their BSI values at a high level of statistical significance in most cases. The ethynylated-11 beta-methoxy analog [18F]-8a had high selectivity (uterus to blood ratio) after 3 h and exhibited the highest uterine uptake (percent injected dose/gram) of any fluorine-substituted estradiol ligand we have studied to date. This compound has been chosen for more detailed studies (to be described elsewhere), including clinical trials in human patients diagnosed with primary breast cancer.

Animals↗
PubMed1993

Progestin 16 alpha, 17 alpha-dioxolane ketals as molecular probes for the progesterone receptor: synthesis, binding affinity, and photochemical evaluation.

Chemical probes for steroid receptors have proven useful in providing molecular details about important hormone-receptor interactions. A series of progestin 16 alpha, 17 alpha-dioxolane ketals of acetophenone or substituted acetophenones that bind to the progesterone receptor (PgR) with comparable or higher affinities than the natural ligand, progesterone, have been prepared and evaluated as potential in vitro and in vivo probes for the progesterone receptor. p-Azidoacetophenone ketal 6, the tetrafluoro analog 8, and the p-(benzoyl)acetophenone ketal 9 demonstrate the required combination of high relative binding affinity (RBA) (6 = 15%, 8 = 14%, 9 = 6.6%, progesterone = 13%, R5020 = 100%) and photoinactivation efficiency (6 = 80%, 8 = 77%, 9 = 29% at 30 min) required for potential photoaffinity labeling reagents for the PgR. The synthesis of azide 6 has been modified to accommodate a palladium-catalyzed tritium gas hydrogenolysis of an iodoaryl precursor in the final stage of the synthetic sequence; this procedure has been verified by hydrogenation. In addition, the progestin p-fluoroacetophenone ketal 10 was selected for preparation in fluorine-18-labeled form, on the basis of its high affinity for the PgR (RBA = 53%). Fluorine-18-labeled progestins may be evaluated as potential diagnostic imaging agents for PgR-positive breast tumors. The radiochemical syntheses and further biochemical results with the fluorine-18-labeled ketal 10 and the tritium-labeled aryl azide 6 will be presented in an accompanying paper and elsewhere.

Affinity Labels↗
PubMed1993

Fluorine-18-labeled progestin ketals: synthesis and target tissue uptake selectivity of potential imaging agents for receptor-positive breast tumors.

We have studied two new fluorine-substituted progestins as potential imaging agents for progesterone-receptor-positive human breast tumors. The steroids are 16 alpha, 17 alpha-fluoroacetophenone ketals of 16 alpha, 17 alpha-dihydroxyprogesterone and 16 alpha, 17 alpha, 21-trihydroxy-19-norprogesterone. Synthesis of the latter compound in seven steps from 19-norandrost-4-ene-3,17-dione is reported. Both compounds demonstrate high affinity for the progesterone receptor (PgR) (52.5 and 240%, respectively, relative to R5020 = 100). The syntheses were adapted to 18F-labeling with 4'-[18F]-fluoroacetophenone, prepared from 4'-nitroacetophenone by nucleophilic substitution with K18F/Kryptofix. Considerable adjustment of reaction conditions was required to effect ketalization using tracer quantities of the ketone. In tissue distribution studies in estrogen-primed immature female rats, both ketals showed selective uterine uptake, which was blocked by coinjection of a saturating dose of the unlabeled progestin ORG 2058. Additionally, metabolic stability of the radiolabel was indicated by the low radioactivity levels seen in bone. Both compounds showed relatively high uptake in fat, in accord with their relative lipophilicities demonstrated by HPLC-derived octanol-water partition coefficients. The selective uterine uptake and metabolic stability of these compounds suggests that this class of PgR ligands might be promising for the selective imaging of receptor-positive tumors if derivatives of reduced lipophilicity can be prepared.

Adipose Tissue↗
PubMed1993

16 beta-[18F]fluoromoxestrol: a potent, metabolically stable positron emission tomography imaging agent for estrogen receptor positive human breast tumors.

16 beta-[18F]Fluoromoxestrol (beta FMOX, 1) is a highly selective, metabolically stable estrogen with potential as a receptor imaging agent. It demonstrates receptor-mediated uptake in the immature rat in the estrogen receptor-rich primary target tissues, uterus and ovaries, as well as, in receptor-poor secondary target tissues, muscle, thymus and kidneys; uptake in the uterus is nearly four times that of the clinically useful 16 alpha-[18F]fluoroestradiol (FES), most likely due to the extended lifetime of the labeled beta FMOX in the blood afforded by its relatively slow metabolism. In vivo and in vitro studies demonstrate a nearly four-fold decrease in metabolism rate between beta FMOX and FES. Dosimetry studies indicate radiation absorbed doses comparable to FES. beta FMOX possesses desirable imaging characteristics and may prove to be a clinically useful imaging agent.

Animals↗
PubMed1993

The effect of acceptor group variation on the solvatochromism of donor-acceptor fluorophores.

The absorption and emission characteristics of five hydroxytetrahydrochrysenes substituted with acceptor groups (nitro, cyano, methylketone, 1 degree amide and methyl ester) (THC-NO2, THC-CN, THC-COCH3, THC-CONH2 and THC-CO2CH3, respectively) were investigated in an extensive set of solvents. The order of absorption and fluorescence bathochromicity are: THC-NO2 > THC-COCH3 > THC-CN > or = THC-CO2CH3 > THC-CONH2 and THC-NO2 >> THC-COCH3 > THC-CO2CH3 > THC-CN > THC-CONH2, respectively. The emission spectra of these compounds are sensitive to the solvent polarity (ET[30] scale) in the order: THC-NO2 > THC-COCH3 > THC-CO2CH3 > THC-CONH2 > THC-CN. The response of the emission maxima of these compounds to the solvent polarity and hydrogen-bond donor/acceptor properties (pi */alpha/beta and acity/basity scales) was also determined. The emission energies of THC-NO2 were most sensitive to pi *, beta, acity, and basity of the solvent; those of the amide were least sensitive to the solvent pi *, beta, and basity. The ground- and excited-state dipole moments were determined by semiempirical molecular orbital calculations and the absorption/fluorescence solvent-shift method, respectively. THC-NO2 had the largest ground- and excited-state moments. The ester and amide had the smallest ground- and excited-state moments, respectively. In general, unsatisfactory results were obtained for correlations of the emission and absorption energies, fluorescence solvatochromism and the ground- and excited-state dipole moments with the Hammett substituent constants of the five acceptor groups. Acceptable correlations were obtained for the absorption and emission energies and the fluorescence solvatochromism with the substituent constants if the cyano compound was excluded.

Chrysenes↗
PubMed1992

Donor-acceptor tetrahydrochrysenes, inherently fluorescent, high-affinity ligands for the estrogen receptor: binding and fluorescence characteristics and fluorometric assay of receptor.

We have examined the binding behavior and fluorescence characteristics of a series of novel ligands for the estrogen receptor (ER). These ligands are derivatives of 5,6,11,12-tetrahydrochrysene (THC), a structure that embodies a stilbene chromophore, found in many nonsteroidal estrogens, within a rigid tetracyclic system where it cannot easily be distorted from planarity, thus providing the conjugation and rigidity required for efficient fluorescence. Additional steric bulk, as trans-disposed ethyl substituents at the internal C-5 and C-11 positions, is required for the highest relative binding affinity (RBA), and the trans-5,11-diethyl-2,8-dihydroxy-THC derivative binds to ER with an affinity greater than that of estradiol. The replacement of one of the phenolic hydroxyl groups of this THC derivative with an electron-withdrawing group (COMe, COOMe, CONH2, CN, or NO2) yields unsymmetrical THCs with binding affinities 15-40% that of estradiol (E2). The fluorescence emission shifts from about 380 nm for the dihydroxy THC to 475-688 nm for the donor-acceptor THCs. The emission of these donor-acceptor THCs is highly solvatochromic and shifts to longer wavelengths as the solvent polarity increases. In ethanol, the fluorescence quantum yield of the first four of these compounds is high (phi f = 0.43-0.69), but the fifth compound, the nitro-THC, is almost nonemissive in protic solvents. When they are incubated with protein solutions containing ER (approximately 10(-9) M), the emission from the donor-acceptor THCs bound specifically to ER is in the 500-570-nm range, whereas fluorescence from non-receptor-bound fluorophores is in the 425-460-nm range. Thus, fluorescence from these probes bound specifically to ER could be measured under equilibrium conditions as well as after the removal of free and non-receptor-bound material by treatment with charcoal-dextran. This is one of the first demonstrations of ligands whose fluorescence is distinctly different when free, when bound to ER, or when bound to non-receptor proteins. It is also the first demonstration of ER assay by fluorescence under equilibrium conditions.

Animals↗
PubMed1992

Synthesis of high affinity fluorine-substituted ligands for the androgen receptor. Potential agents for imaging prostatic cancer by positron emission tomography.

We have prepared nine androgens substituted with fluorine at C-16 or C-20 to evaluate their potential, as positron emission tomographic (PET) imaging agents for prostatic cancer when labeled with the positron emitting radionuclide fluorine-18 (t1/2 = 110 min). These compounds represent members from the following classes of androgens: testosterone (T), 5 alpha-dihydrotestosterone (DHT), 7 alpha-methyl-19-nortestosterone (MNT), mibolerone (Mib), and metribolone (R1881). All of these compounds were prepared by functionalization of suitable androgen precursors, and the synthetic routes were developed to allow the introduction of fluorine by a fluoride ion displacement reaction late in the synthesis, as is required for the preparation of these compounds in fluorine-18 labeled form. We have also prepared four androgens in which the C-3 carbonyl or 17 beta-hydroxyl groups are replaced by fluorine. Most of the fluorine-substituted androgens show high affinity for the androgen receptor (AR), although fluorine substitution lowers their affinity by a small factor. None of the androgens where fluorine replaces oxygen functions at C-3 or C-17 have substantial affinity for AR. Derivatives of the natural androgens (T and DHT) as well as MNT have little affinity for other steroid hormone receptors (progesterone and mineralocorticoid receptors), whereas the Mib and R1881 derivatives have somewhat greater heterologous binding. With sex steroid binding protein, a human serum binding protein, the pattern of binding affinities is nearly the reverse, with derivatives of Mib, R1881 and MNT having low affinity, and DHT and T, high affinity. From these fluorine-substituted compounds, we can select several whose preparation in fluorine-18 labeled form for further tissue distribution studies is merited.

Androgens↗
PubMed1992

Nonsteroidal estrogens bearing acyl azide functions: potential electrophilic and photoaffinity labeling agents for the estrogen receptor.

In an effort to develop novel affinity labeling agents for the estrogen receptor, we have synthesized two nonsteroidal ligands, a 1-aroyl-2-aryl tetralin system (1) and a 2-aryl-3-aroylbenzo[b]thiophene system (2). These agents, patterned after the Lilly antiestrogens trioxifene and LY 117018, respectively, embody acyl azide functions as part of a benzoyl chromophore. The acyl azide group has weak acylating activity, suitable for electrophilic affinity labeling, but this function is also photoreactive and, in its particular embodiment within these ligands, it could provide an efficient photochemical route to the highly reactive singlet acyl nitrene. The tetralin system (1) was prepared in nine steps from 6-methoxy-1-tetralone, and the benzothiophene system (2) was prepared in four steps from a known substituted benzo[b]thiophene precursor. In competitive binding assays, both compounds show reasonable binding affinity for the rat and lamb uterine estrogen receptor: estradiol = 100%, 1 = 3%, and 2 = 12%. When assayed by indirect receptor consumption assays, both compounds appear to have substantial capacity for irreversible binding (electrophilic reaction) with the receptor. This reactivity, which suggests that acylation of the receptor has occurred, is photoreversible. The nature of this ligand-receptor interaction is being investigated further.

Affinity Labels↗
PubMed1992

Preparation and evaluation of 17-ethynyl-substituted 16 alpha-[18F]fluoroestradiols: selective receptor-based PET imaging agents.

We have prepared and studied six new analogs of 16 alpha-fluoroestradiol (FES): 17 alpha- and 17 beta-ethynyl-FES (7 [FEES] and 7a), and the 11 beta-ethyl (8 and 8a) and 11 beta-methoxy (9 and 9a) derivatives, novel estrogen receptor-based PET imaging agents. The relative binding affinity (RBA) for the estrogen receptor (ER) versus FES is increased for 7, 9 and 9a but decreased for 7a, 8 and 8a. All six analogs have been labeled in the 16 alpha position with 18F by the nucleophilic displacement of the corresponding 16 beta-trifluoromethanesulfonate with nBu4N18F. Subsequent ethynylation with lithium trimethylsilylacetylide yielded the FEES analogs (total synthesis time: 120 min; effective specific activity: 200-2400 Ci/mmol). Selective uptake in the uterus was high for [18F]7, [18F]8, [18F]9 and [18F]9a (% ID/g values at 1 h: 11.2, 12.9, 9.9 and 8.3, respectively), while uptake was effectively blocked by coinjection of an excess of unlabeled estradiol. The FEES analogs, [18F]7, [18F]8 and [18F]9, exhibited the highest selectivity, in terms of target (uterus)-to-blood ratios, ever seen amongst estrogen radiopharmaceuticals, 154, 145 and 169, respectively. The analogs [18F]7a and [18F]8a displayed no uptake in the uterus, consistent with their low RBAs. Metabolism studies revealed that most of the uterine activity is unmetabolized while the blood exhibits a rapid and subsequently sustained mixture of metabolites. The muscle shows a metabolic profile intermediate to the uterus and blood. These analogs provide an array of desirable characteristics for the optimal PET imaging of ER-rich target tissues.

Animals↗
PubMed1992

Fluorine-substituted corticosteroids: synthesis and evaluation as potential receptor-based imaging agents for positron emission tomography of the brain.

We have prepared eight fluorine-substituted corticosteroids representing ligands selective for Type I and Type II corticosteroid receptor subtypes as potential imaging agents for corticosteroid receptor-containing regions of the brain. Receptor binding affinity assays show that fluorine substitution for hydroxyl or hydrogen in these steroids generally results in some reduction in affinity, with the result that the absolute affinity of these fluorine-substituted ligands for receptor is less than that typical for steroid hormones that show receptor-based, target selective uptake in vivo. Five of these compounds were prepared in fluorine-18 labeled form by a simple sulfonate ester displacement reaction, and their tissue distribution was studied in the adrenalectomized rat. There is no selective accumulation nor selective retention of the Type I selective corticosteroids (18F-RU 26752, 21-[18F]fluoroprogesterone, 21-[18F]fluoro-11 beta-hydroxyprogesterone) in either the brain, or other target tissues (pituitary, kidney, liver). The Type II selective corticosteroids (18F-RU 28362, 18F-triamcinolone acetonide) show uptake into the hippocampus which can be partially blocked by a competing ligand; in target tissues outside the brain, the blocking is more complete. All of the 18F-labeled compounds show considerable defluorination, evident as high bone activity levels. These results, coupled with earlier findings in the literature, suggest that radiolabeled corticosteroid receptor ligands with both greater metabolic stability and higher receptor binding affinity and selectivity are needed for imaging corticosteroid receptors in the hippocampus.

Adrenal Cortex Hormones↗
PubMed1992

Estrogen platinum-diamine complexes: preparation of a non-steroidal estrogen platinum-diamine complex labeled with platinum-191 and a study of its binding to the estrogen receptor in vitro and its tissue distribution in vivo.

We have prepared in radiolabeled form (platinum-191) a non-steroidal estrogen platinum-diamine complex (Pt-diamine complex) that is reported to have selective cytostatic activity in estrogen receptor positive mouse mammary tumors. We then studied the interaction of this metal radiolabeled complex with the estrogen receptor in vitro and its distribution in immature rats in vivo. The radiolabeled complex was prepared by incubation of the non-steroidal estrogen diamine with [191Pt](II)Cl(-2)4 (t 1/2 = 2.96 days, sp. act. 7.54 Ci/mmol) in dimethylformamide (DMF)/H2O, followed by purification by HPLC. The final radiolabeled product coeluted with an authentic standard of the unlabeled Pt-diamine complex, with a retention time distinct from those of the precursor diamine and chloroplatinate. In competitive radiometric receptor binding assays with rat uterine estrogen receptor, samples of the unlabeled diamine and Pt-diamine complex have apparent binding affinities of 53 +/- 3% and 32 +/- 11%, respectively, relative to estradiol (RBA = 100% as standard). However, attempts to observe the binding of the 191Pt-diamine complex with the estrogen receptor were complicated by a very high level of non-receptor binding, an irreversible binding to proteins in the receptor preparation, and a degradation of the platinum complex that, in part, releases the diamine. As a result, it is difficult to be certain whether the binding affinity measured for the Pt-diamine complex in the competitive binding assays is due to the complex itself, or whether it arises from diamine released upon degradation of the complex. In tissue distribution studies in immature female rats, much of the 191Pt-diamine complex was deposited in the liver; there was no evidence of selective uptake of this compound by estrogen target tissues. Thus, it is not clear, from these studies, that the observed bioactivity of this complex arises from the interaction of the Pt complex or the diamine ligand with the estrogen receptor.

Animals↗
PubMed1992

Technetium- and rhenium-labeled progestins: synthesis, receptor binding and in vivo distribution of an 11 beta-substituted progestin labeled with technetium-99 and rhenium-186.

In an effort to develop radiopharmaceuticals useful for the diagnostic imaging of steroid receptor-positive breast tumors, we have radiolabeled an analog of the antiprogestin RU486 (mifepristone), modified to incorporate an N2S2 chelate system in the 11 beta-position, with 99Tc, 99mTc, and 186Re. For the 99Tc-labeled analogs (3), a syn pair and two individual antidiastereomers (linker methylene versus metal-oxo, relative to the N2S2 plane) were isolated. In competitive radiometric binding assays, the syn pair (3syn1,2) had affinity for the progesterone receptor that was 25% that of (promegestone) R5020 (or 161% that of progesterone), and the individual anti-diastereomers had affinities of 47% (3anti1) and 7% (3anti2) that of R5020 (or 303% and 45% that of progesterone). The specific-to-nonspecific binding ratio of the 99mTc (4) and 186Re (5) 11 beta-linked syn systems are 75/25 and 54/46, respectively. In vivo, conjugates 4 and 5 showed progesterone receptor-mediated uptake in rat uterus, but also high uptake in non-target tissues, presumably because of the high lipophilicity of the metal complexes. Modified systems may be useful in vivo as receptor-directed agents for diagnostic imaging or treatment of steroid receptor-positive tumors.

Animals↗
PubMed1991

Efficient and selective photoaffinity labeling of the estrogen receptor using two nonsteroidal ligands that embody aryl azide or tetrafluoroaryl azide photoreactive functions.

3-(4-Azido-2,3,5,6-tetrafluorobenzoyl)-6-hydroxy-2-(4- hydroxyphenyl)benzo[b]thiophene 1 (tetrafluoroaryl azide, TFAA) and its protio analogue 3-(4-azidobenzoyl)-6- hydroxy-2-(4-hydroxyphenyl)benzo[b]thiophene 2 (protioaryl azide, PAA), photoaffinity labeling (PAL) reagents for the estrogen receptor (ER), have been prepared in high specific activity tritium-labeled form (19 Ci/mmol) and shown to undergo selective and efficient photocovalent attachment to ER from rat uterus. Both azides 1 and 2 demonstrate high binding affinity for ER as determined by both a competitive binding assay (relative binding affinities: estradiol = 100; TFAA = 9.3; PAA = 66) and a direct binding assay (Kd: estradiol = 0.24 nM; TFAA = 2.64 nM; PAA = 0.37 nM). When unlabeled TFAA and PAA are irradiated at greater than 315 nm, they demonstrate site-specific photoinactivation of ER that reaches 43% and 55%, respectively, by 30 min. Specific photocovalent attachment to ER can be effected by irradiation of the tritium-labeled azides; the covalent attachment efficiency is good (1 = 20-30%, 2 = ca. 25%) and the selectivity of ER labeling is high. Characterization of the photolabeled proteins by SDS-polyacrylamide gel electrophoresis shows specific labeling of a major component at Mr 60,000 and a minor species at Mr 46,000, the same two species that are labeled by [3H]tamoxifen aziridine, a well-characterized affinity label for ER. The ER-specific antibodies H222Sp gamma and D547Sp gamma show a clean precipitation of only these two species. In the MCF-7 human breast cancer cell line, PAA is a full estrogen agonist in terms of stimulation of cell proliferation and induction of progesterone receptor. These two azides provide the first system in which the photocovalent attachment efficiency of an aryl azide can be compared to its tetrafluorosubstituted aryl azide analogue in a complex biological receptor system. Azides 1 and 2 are the most efficient and selective PAL reagents prepared to date for ER, and they should be useful in further studies of the hormone-binding domain of this protein.

Affinity Labels↗
PubMed1990

A comparative study of the selectivity and efficiency of target tissue uptake of five tritium-labeled androgens in the rat.

A comparative study of the tissue distribution of five tritium-labeled androgens was done in rats to determine the efficiency and selectivity of their uptake by target tissue. Testosterone (T), 5 alpha-dihydrotestosterone (DHT), 19-nortestosterone (nor-T), mibolerone (Mib) and methyltrienolone (R1881) all showed selective uptake by the ventral prostate in one-day castrated rats (250 g) that was 61-90% displaceable by co-injection of an excess of unlabeled steroid. The greatest uptake was with R1881 (0.69% injected dose per gram prostate tissue (%ID/g) at 1 h), and Mib (0.56% ID/g); the other three showed lower uptake (approx. 0.4% ID/g). The target tissue activity remained high for all compounds up to 4 h after injection, and at 2-4 h the prostate to blood ratio for Mib and R1881 exceeded 10 and 20, respectively. The uptake efficiency and selectivity of these five androgens appear to be related to their affinity for the androgen receptor and their resistance to metabolism. Mib and R1881 have substantial affinity for other steroid receptors, which might account for some of their prostate uptake. However, co-administration of triamcinolone acetonide, which has high affinity for progesterone and corticosteroid receptors but not for the androgen receptor, failed to block their uptake significantly, whereas co-administration of DHT, the most selective ligand for the androgen receptor, blocked their uptake as completely as the unlabeled tracer itself. The prostate uptake of Mib and R1881 in intact animals was significantly lower than in castrated animals, but treatment of the intact animals with diethylstilbestrol restored their uptake nearly to the level seen in castrated animals. These uptake patterns are consistent with earlier studies of in vivo androgen uptake and with known changes in androgen receptor content and occupancy as a result of castration or diethylstilbestrol treatment. They further suggest that high affinity androgens labeled with suitable radionuclides--particularly derivatives of mibolerone (Mib) or methyltrienolone (R1881)--may be effective receptor-based imaging agents for androgen target tissues and tumors, even when patients are already receiving hormonal therapy.

Androgens↗
PubMed1990

[3H]DU41165: a high affinity ligand and novel photoaffinity labeling reagent for the progesterone receptor.

17 alpha-Acetoxy-6-fluoro-16-methylene-(9 beta, 10 alpha)pregna-4,6-dien- 3,20-dione (DU41165), a retroprogestin (9 beta, 10 alpha) embodying a fluorine-substituted dienone system, has been prepared in high specific activity tritium-labeled form (4 Ci/mmol) and shown to be a high affinity ligand for the progesterone receptor (PgR) and a highly selective photoaffinity labeling reagent for PgR. The radiosynthesis involved conversion of DU41231 (the 17 alpha-hydroxy analog of DU41165) to DU41165 by treatment with tritium-labeled acetic anhydride. The binding affinity of DU41165 for PgR was determined by both a competitive binding assay and a direct binding assay (Scatchard analysis) to be 1.6-2.2-times higher than that of the high affinity synthetic progestin promegestone (R5020). In unlabeled form, DU41165 demonstrates photoinactivation of PgR to the extent of 60% at 60 min. In radiolabeled form [3H]DU41165 demonstrates specific covalent attachment with an efficiency of 5-7%. SDS-polyacrylamide gel electrophoresis of photoattached [3H]DU41165 confirms that there is covalent labeling of both the B subunit (Mr = 118,000), and the A subunit (Mr = 88,000) of PgR in a molar ratio of approximately 1:3.

Affinity Labels↗
PubMed1990

Target tissue uptake selectivity of three fluorine-substituted progestins: potential imaging agents for receptor-positive breast tumors.

We have studied three new fluorine-substituted progestins (1-3) as potential imaging agents for progesterone receptor (PgR)-positive human breast tumors. Two of these are fluorine-substituted analogs of the potent progestin R5020 (promegestone), derived from (21S)-hydroxy R 5020 (RU 27987) and (21R)-hydroxy R 5020 (RU 27988), known metabolites of R 5020, which have affinities for PgR that are 116 and 4%, respectively (relative to R 5020 = 100%). These precursors were protected as their 3,3-dioxolane derivatives and converted to the 21-trifluoromethanesulfonate derivatives. Fluoride ion displacement, followed by acid-catalyzed deprotection, furnished in good yield the epimeric fluoroanalogs, (21S)- and (21R)-fluro R 5020 (1 and 2, affinities for PgR, 11 and 45%, respectively). These compounds were also prepared in 18F labeled form by the same route, in 14-32% overall radiochemical yield (decay corrected; synthesis time 90 min; sp. act. 370-1060 Ci/mmol). In tissue distribution studies in estrogen-primed immature rats, uterus-to-muscle ratios were 4.3 at 1 h for the 21S-epimer and 1.1 for the 21R-epimer, paralleling their relative binding affinities. Considerable metabolic defluorination was observed. The third fluorine-substituted progestin, DU 41165, has a novel retroprogesterone (9 beta, 10 alpha) structure, substituted with fluorine at C-6; its binding affinity is 145% relative to R 5020, and it was prepared in tritium-labeled form by acetylation of DU 41231, the 17 alpha-hydroxy precursor, with [3H]acetic anhydride. In estrogen-primed immature rats, this compound shows uterus-to-muscle ratios of 15 at 1 h, and 18-71 between 2 and 6 h, suggesting that compounds in this retroprogesterone series may be very promising candidates for selective imaging of PgR-positive tissues and tumors.

Animals↗
PubMed1990

11 beta-methoxy-, 11 beta-ethyl- and 17 alpha-ethynyl-substituted 16 alpha-fluoroestradiols: receptor-based imaging agents with enhanced uptake efficiency and selectivity.

We have prepared three analogues of 16 alpha-fluoroestradiol (FES) substituted either with an 11 beta-methoxy group (1, 11 beta-MeO-FES), an 11 beta-ethyl group (2, 11 beta-Et-FES), or a 17 alpha-ethynyl group (3, 17 alpha-ethynyl-FES). These substituents all lower the binding of FES to the serum proteins alphafetoprotein and sex steroid binding protein, but their effect on estrogen receptor binding varies: Receptor binding is increased by the 11 beta-ethyl and 17 alpha-ethynyl groups, but decreased by the 11 beta-methoxy group. These substituents also have a parallel effect on the lipophilicity, and hence the nonspecific binding estimated for these compounds. All three compounds were prepared in fluorine-18 labeled form, at effective specific activities of 90-1600 Ci/mmol, by fluoride ion displacement reactions as done previously with FES. Tissue distribution studies in immature rats show high uptake selectivity by target tissue (uterus) and effective competition by an excess of unlabeled estradiol. Percent injected dose per gram values (% ID/g) at 1 h are 6% for 11 beta-MeO-FES and 11-13% for 11 beta-Et-FES and 17 alpha-ethynyl-FES (FES itself has a % ID/g of 9%). Uptake selectivity in terms of uterus to blood or muscle ratios at 1 h is highest for 11 beta-MeO-FES and 17 alpha-ethynyl-FES (43-149). Metabolic consumption studies show that most activity in uterus is unmetabolized and in blood is rapidly and nearly completely metabolized. In muscle, FES and the substituted estrogens show intermediate levels of metabolic consumption; in some cases activity in muscle extracts is nearly unmetabolized. Thus, the substituents on FES cause major alterations in receptor and nonreceptor binding affinity, uptake efficiency and selectivity, and extent of metabolism. It is not readily clear, however, whether the alterations in uptake efficiency and selectivity are the result of differences in receptor or nonreceptor binding or lipophilicity, or altered patterns of metabolism. Nevertheless, these compounds should be useful in providing a spectrum of uptake properties that could be used for imaging different estrogen-receptor-containing structures.

Animals↗