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Biomedical subjects

V Petrow

Publications and source records attributed to V Petrow.

At least 37 records · Page 2Linked to original sources
PubMed1989

Prostate. III--A structural feature characteristic of the rat prostate 5 alpha-reductase active site.

To aid in the design of new inhibitors of steroidal 5 alpha-reductase for treatment of prostate cancer, we have studied the topography of the 5 alpha-reductase active site (5 alpha-R) and of the related androgen (RA) and progesterone (RP) receptors in the region complementary to C.6 of progesterone. To this end we have determined the total structures of 17 alpha-acetoxy-6-methylene-4-pregnene-3,20-dione (VII; R = H) and of 17 beta-hydroxy-6,6-ethylene-4-androsten-3-one (VIa) by X-ray crystal structure analysis and, using these data, have developed Newman projections of the 6 alpha-Me, 6 beta-Me, 6-methylene and 6,6-ethylene derivatives of progesterone. From them we have developed a Newman projection of a composite model formed from steroids (V), (VI), (VIIIa) and (VIIIb). This is shown in Fig. 4 and illustrates the relative conformations of these substituents around C.6. From there we proceeded to receptor-binding studies. Our results led to the conclusion that androgen receptor, (RA), takes up preferred but different conformations when bound to testosterone (T) and to 17 beta-hydroxy-5 alpha-androstan-3-one (5 alpha-dihydrotestosterone, DHT), respectively, and that the resulting steroid-receptor complexes bind preferentially to different chromatin acceptor sites. We have therefore used the convention RT and RDHT in place of RA as appropriate. Working on the assumption that binding affinities reflect spatial contours, we have developed comparative silhouettes for the 5 alpha-R, RP and RDHT protein binding sites complementary to C.6 of the steroidal ligand. These data show that the 5 alpha-reductase active site is characterized by a hydrophobic pocket which specifically accommodates a 6-methylenic moiety and partially accommodates a 6 beta-methyl group. RDHT, in contrast, shows much less specificity and largely accommodates all the above substituents. Progesterone receptor differs in failing to accommodate 6,6-ethylene and 6 beta-methyl, with minimal accommodation of 6-methylene. It possesses a hydrophobic pocket skewed towards the alpha-face of the steroid, thereby allowing optimal binding of the 6 alpha-methyl substituent to the receptor. 6-Methylene-4-pregnene-3,20-dione (V) fails to bind significantly to androgen and progesterone receptors thereby supporting the postulate that its antiprostatic activity stems primarily from 5 alpha-reductase inhibition.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1989

A new approach to prostate cancer.

Growth of androgen-dependent human prostatic adenocarcinoma implanted in the nude mouse (Honda tumour), is inhibited by 6-methyleneprogesterone. This steroid is a potent inhibitor of both rat and human prostatic 5 alpha-reductase in-vitro. In-vivo, at the studied dose level, it reduces metabolic conversion of testosterone to dihydrotestosterone with minimal effects upon circulating LH and testosterone. These data support the hypothesis that dihydrotestosterone and not testosterone is the main trophic androgen of the human prostatic neoplasm.

Adenoma↗
PubMed1988

The effects of an aromatase inhibitor and a 5 alpha-reductase inhibitor upon the occurrence of polyovular follicles, persistent anovulation, and permanent vaginal stratification in mice treated neonatally with testosterone.

Female C57BL/Tw mice were given 5 daily injection of 20 micrograms testosterone (T), 100 micrograms 4-hydroxy-4-androstene-3, 17-dione (4-HA), 100 micrograms 6-methylene-4-pregnene-3, 20-dione (6-MP), 4-HA + 6-MP, T + 4-HA, T + 6-MP, and T + 4-HA + 6-MP starting on the day of birth. The animals were ovariectomized at 30 days or 90 days of age and were killed at 150 days. The incidence of polyovular follicles (PF) at 30 days of age was significantly increased by neonatal treatment with T. By contrast, the PF incidence was significantly reduced by injections of 4-HA given simultaneously with T. Neonatally T- or T + 6-MP-treated 90-day-old mice had ovaries containing follicles and hypertrophied interstitial cells but no corpora lutea. By contrast, T + 4-HA (64%)- and T + 4-HA + 6-MP (82%)-treated mice had ovaries with corpora lutea. In the T + 4-HA + 6-MP (82%)-treated mice had ovaries with corpora lutea. In the T + 4-HA + 6-MP-treated, 150-day-old, ovariectomized mice, the number of mice showing vaginal epithelial stratification was significantly decreased as compared with T-treated mice. There were no significant differences in the number of layers, thickness, and mitotic rate of vaginal epithelium of T-treated mice compared with mice treated with T + 4-HA, T + 6-MP, or T + 4-HA + 6-MP. The present results indicate that development of PF and persistent anovulation are due to the direct action of estrogen (E) derived from T upon neonatal ovarian follicles and the neonatal hypothalamo-hypophysial system, and that T itself can induce ovary-independent vaginal changes, although 5 alpha-reduced androgen and estrogen derived from T seem to be more effective in this regard.

5-alpha Reductase Inhibitors↗
PubMed1987

Aromatase activity in microsomes from rat ventral prostate and Dunning R3327H rat prostatic adenocarcinoma.

We have measured aromatase activity in microsomes obtained from rat ventral prostate, using the 3H2O release method as described by Weisz. Production of 3H2O from 1 beta-[3H]androstenedione correlated with estrogen production measured by RIA and by TLC. The assay was optimized for incubation time and protein concentration, and used to determine the aromatase activity of ventral prostate microsomes from rats of varying age. Aromatase activity per mg microsomal protein increased from an average of 4 pmol/mg protein X h in 3-month old rats to 68 pmol/mg protein X h in 8-month old rats. Aromatase activity was also measured in microsomes from the Dunning R3327H rat prostatic adenocarcinoma, and was increased in tumors removed 225 days after implantation compared to tumors removed 141 days after implantation. Tumors removed 225 days after implantation from rats which had been treated with DES for 14 days displayed increased aromatase activity compared to untreated tumors. The presence of aromatase activity in the rat ventral prostate and rat prostatic adenocarcinoma would allow regulation of estrogen levels independent of circulating estrogen. Thus, in situ changes in estrogen production with age may contribute to the development of prostatic disease.

Adenocarcinoma↗
PubMed1987

Steroid-induced ocular hypertension in the rabbit: a model using subconjunctival injections.

Topical application of glucocorticoids in rabbit eyes has been used extensively in the study of steroid-induced ocular hypertension. Herein, we report no difference in intraocular pressure (IOP) between rabbits treated with topically applied dexamethasone and those receiving a vehicle placebo. In order to develop an alternative model, we have studied the effects on IOP of three subconjunctivally injected steroids: betamethasone, cortisone, and triamcinolone. All three produced elevations in IOP above controls and the most consistent elevation was observed with triamcinolone. Previously, a wide range of changes in IOP have been regarded as significant in studies using the topical mode. Our findings suggest that subconjunctival injections of steroids in rabbits are a viable alternative to topical application and may prove to provide a more consistent and reproducible model for the study of steroid-induced ocular hypertension.

Animals↗
PubMed1987

A comparison of the effects of castration and 6-methylene progesterone, a 5 alpha-reductase inhibitor, on the rat ventral prostate.

6-Methylene progesterone (6MP) is an irreversible in vitro kcat inhibitor of rat prostate 5 alpha-reductase, the enzyme which converts testosterone (T) to dihydrotestosterone (DHT). Treatment of adult rats with 6MP or diethylstilbestrol (DES) decreased the weight of the ventral prostate (VP) by 45%, while castration reduced it by 86%. Histologically, the 6MP-treated VP were indistinguishable from those of controls, while the VP from DES-treated rats showed fibrous stromal hypertrophy as in castrated rats. The prostatic hydroxyproline content, an index of collagen levels, was enhanced by castration or DES, but was not significantly increased by 6MP. Within 2 days of 6MP treatment, the 5 alpha-reductase activity was reduced by 46% and ornithine decarboxylase (ODC) activity was lowered by 27%. During this time the prostatic acid phosphatase activity increased 42% and remained elevated with continued exposure to 6MP up to 13 days. The castration-induced involution of the VP was accompanied by a reduction in serum T and an increase in serum luteinizing hormone (LH). 6MP had no effect on T and LH serum levels but reduced the DHT content within the VP by 64%. Our results indicate that the structure and secretory acid phosphatase activity of the VP are less sensitive to changes in the ratio of T:DHT than is cell proliferation. Thus, the relative amounts of DHT and T within the VP may prove to be more significant than the absolute amount of either androgen in controlling prostate growth or its attendant neoplasms.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1987

Androgen receptor, testosterone uptake and karyotype in androgen-dependent mouse tumor (SC 115) and its androgen-independent subline (CS 2).

Content of androgen receptor, retention of injected testosterone and karyotype of SC 115, androgen-dependent tumor, were compared with those of CS 2, an androgen-independent subline derived from SC 115. Although Bmax was less than that of SC 115, androgen receptor was present in the cytosol and the nuclear extract from CS 2. To examine the ability for androgen retention, a large amount of testosterone was injected into tumor-bearing mice, and the amount of androgen in the crude nuclear and postnuclear fractions of tumors was compared. In both fractions, retention of injected androgen was higher in the SC 115 than in the CS 2. Since most of the injected testosterone was not metabolized in the tissues and the injection of testosterone 5 alpha-reductase inhibitor showed no significant influence on the growth rate of the SC 115, intracellular active androgen was assumed to be testosterone in these tumor cells. As the CS 2 was tetraploid, the androgen independency of the CS 2 seems to be related to chromosomal changes.

Animals↗
PubMed1986

Design of cytotoxic steroids for prostate cancer.

Our object was to determine if the aromatic nucleus of estramustine (I) is optimal for binding affinity to prostate cytosolic proteins, and if C3 is the preferred position for the N-mustard carbamate moiety. To this end we have submitted 34 steroids for in vitro assay of binding affinity to total prostate cytosolic proteins. Our structures included aromatic and hydroaromatic steroids containing N-mustard carbamate and other substituents at C3, C6, C11, C16, C17, C20, and C21. Our results show that binding affinity to prostate proteins is optimally present in C3-nitrogen mustard carbamates attached directly to a totally planar aromatic ring as in (IV). Partial deviation from total planarity as in enol-carbamates (V) leads to some loss of binding affinity, which largely disappears in hydroaromatic structures (VI). Thus, our data lead to the Ring A aromatic structure (X) as a basis for the design of steroidal N-mustard carbamates with prostate selectivity. Preliminary in vivo studies using the Dunning R3327AT prostatic adenocarcinoma implanted in the Copenhagen rat generally support our in vitro data.

Adenocarcinoma↗
PubMed1986

The dihydrotestosterone (DHT) hypothesis of prostate cancer and its therapeutic implications.

Data are presented showing that human prostatic adenocarcinoma depends on dihydrotestosterone (DHT) and not testosterone (T) for growth. It follows that androgen ablative therapy should be directed toward elimination of DHT with retention of circulating T. This can be achieved by using a 5 alpha-reductase inhibitor such as 6-methyleneprogesterone (6-MP) (VII). Arguments are presented showing that 6-MP (VII) is expected 1) to function as a prophylactic agent against prostate cancer, 2) to represent an attractive therapeutic modality for palliative treatment of the hormone-responsive disease, and 3) to be compatible with other therapeutic modalities when very low prostatic levels of DHT should be within reach.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1985

Approaches to prostatic cancer chemotherapy using the Dunning R3327H prostatic adenocarcinoma.

Androgen-responsive cells: To determine if testosterone or dihydrotestosterone is the main trophic hormone of prostatic adenocarcinoma, we have treated Dunning R3327H prostatic adenocarcinoma-bearing rats with 6-methylene progesterone, which blocks conversion of testosterone to dihydrotestosterone. Copenhagen-Fisher rats were treated with steroid (20 mg/Kg daily) immediately following implantation of tumor and thereafter for 117 days. There was a 92% inhibition of growth of tumors and a lesser effect upon prostate and seminal vesicles. Tumor-free body weights remained unchanged. Both treated and untreated tumors had equivalent DNA content on a per weight basis. This result supports the thesis that prostatic adenocarcinoma requires dihydrotestosterone for growth. Androgen-insensitive cells: Advanced prostate cancer does not respond to endocrine therapy but is temporarily controlled by the cytotoxic steroid estramustine. The latter shows significant selective binding to prostatic protein. To develop chemotherapeutic agents that will control androgen-insensitive cells and possess improved selectivity for prostatic protein, we have studied a number of steroids for their ability to displace 3H-labeled estramustine from prostatic cytosolic proteins. Surprisingly, a carbamido substituent at the C17 position was found to confer significant binding affinity for prostatic estramustine-binding protein. Extension of this structural characteristic to the estramustine type of molecule is being studied.

5-alpha Reductase Inhibitors↗
PubMed1984

Comparative studies of 5 alpha-reductase inhibitors within MCF-7 human breast cancer cells.

We have compared the inhibitory effects of six synthetic steroid analogs (17 beta-carboxy-4-androsten-3-one benzylanilide (VP-1), 17 alpha-acetoxy-6-methylene-4-pregnene-3,20-dione (VP-2), 6-methylene-4-pregnene-3,20-dione (VP-3), 17 beta-acetoxy-6-methylene-4-androsten-3-one (VP-4), 17 beta-acetoxy-16,16-dimethyl-6-methylene-4-androsten-3-one (VP-5), and 3 beta-hydroxy-16-methylene-5-androsten-17-one (VP-6) ) upon 5 alpha-reductase activity within MCF-7 human breast cancer cells and rat prostate. Enzyme assays were performed by quantifying the amounts of [3H]5 alpha-androstan-3 alpha-17 beta-diol and/or [3H]dihydrotestosterone formed from 40 nM [3H]testosterone within each system. Five microM concentrations of VP-2 and VP-3 inhibited prostatic 5 alpha-reductase by 55 and 65%, respectively, whereas the other analogs showed little activity. In contrast, each of the six analogs was active against MCF-7 homogenate 5 alpha reductase activity. VP-2 and VP-4 demonstrated approx 65 and 70% inhibitions, respectively, whereas the other four compounds inhibited enzyme activity by 40-55% in this system. These results suggest that rat prostate and MCF-7 cells contain different 5 alpha-reductase isozymes. When these agents were examined for 5 alpha-reductase inhibitory activity following 1 h preincubations with intact MCF-7 cultures, VP-1 and 3 demonstrated potencies similar to those in MCF-7 homogenate. The other compounds, however, were far less active under these conditions. Longer culture preincubations (16 h) were associated with substantially increased VP-6 potency, moderate increases for VP-4 and 5, but no change in VP-2 activity. Additional studies examining the abilities of these agents to bind to MCF-7 androgen receptor (AR) and progesterone receptor (PR) revealed moderate AR binding activities of VP-2, 3, and 4, and substantial PR binding for VP-2 and 3. Finally, VP-4 failed to inhibit estrogen-dependent MCF-7 PR synthesis, suggesting that it has no androgenic activity despite its ability to interact with MCF-7 AR.

5-alpha Reductase Inhibitors↗
PubMed1983

Endocrine properties of RMI 12,936, an antiprogestational steroid.

RMI 12,936 (17 beta-hydroxy-7 alpha-methyl-5-androstene-3-one) exhibited postcoital contragestative activity at 10 mg/kg in hamsters. The endocrinological profile was determined for this steroid. This antifertility agent had significant antiprogestational, antiuterotrophic and gonadotropin-inhibiting activity. RMI 12,936 also exhibited weak uterotrophic and androgenic properties when given to immature gonadectomized rats. Hormonal antagonism and weak estrogen agonist properties would appear to contribute to the contragestative activity of RMI 12,936 in hamsters.

Androstenols↗
PubMed1983

Inhibitory effects of some steroidal 6-methylene derivatives on 5 alpha-reductase activity in human and rat prostate.

Using a short-term organ culture assay, some 6-methylene derivatives of progesterone and testosterone have been evaluated for their effects on testosterone metabolism in rat and human prostatic tissues, and on DNA synthesis in explants from 7-day castrated rats. Comparative studies showed that the ability to inhibit 5 alpha-reductase activity was fairly specific with respect to structural requirements. Methylene substitution at the C6 position of the progesterone molecule was associated with high inhibitory activity. In explants prepared from human prostates, 6-methylene progesterone (II) had 70-85% (mean of 79% for 4 BPH tissues) of the potency of unmodified progesterone (I). Its 17 alpha-acetoxy-6-methylene analog (III), however, had only 32-73% (mean of 53% for 5 BPH specimens) of the activity of (I). The degrees of inhibition in rat and human prostatic tissues were similar. Inhibition of 5 alpha-reductase activity in cultured explants by 6-methylene progesterone (II) could not be reversed by change in media. The 6-methylene derivatives had little or no effect on DNA synthesis. Histological examination confirmed a lack of effect on basal cell proliferation. However, morphological alterations affecting epithelial cell height and secretory activity were clearly evident. These results indicate that, under our experimental conditions, the main effect of inhibition of 5 alpha-reductase activity in prostatic tissues by 6-methylene derivatives of progesterone is related to suppression of differentiated function.

5-alpha Reductase Inhibitors↗
PubMed1983

Prostatic cancer--II. Inhibitors of rat prostatic 4-ene-3-ketosteroid 5 alpha-reductase derived from 6-methylene-4-androsten-3-ones.

The studied 6-methylene-4-androsten-3-ones proved to be significantly inferior to 6-methylene-4-pregnene-3,20-dione and its 17-acetoxy derivative described in Part 1 as inhibitors of 4-ene-3-ketosteroid 5 alpha-reductase [1] in vitro. Surprisingly, the 6-methylene derivative of testosterone was only weakly active until acetylated, when an effective inhibitor was obtained. Etherification of the hydroxyl-group, its replacement by a hydrocarbon chain, or introduction of a substituent at C17 or on the methylene group led to virtual loss of activity. 17 alpha-Chloro-6-methylene-4-androstene-3-one had ca 60-70% of the potency of progesterone, but was inactive as enzyme inhibitor in explants of rat prostate in tissue culture and in in vivo studies. 6-Methylenetestosterone acetate was weakly active as enzyme inhibitor in explants of human prostate in tissue culture and produced a histological picture closely resembling testosterone and differing from that of cyproterone acetate. In vivo in the rat it had 80% of the androgenic activity of testosterone propionate. The foregoing data have been used to define some structural characteristics necessary for enzyme inhibition and to draw some conclusions regarding the architecture of the androgen and progesterone receptors and of the enzyme active site.

5-alpha Reductase Inhibitors↗
PubMed1983

Effect of the preestrogen 4-androstene-3,17-dion-19-al on the Dunning R3327 prostatic adenocarcinoma.

The purpose of this pilot study was to determine if biogenetic precursors of estrone such as 4-androstene-3,17-dion-19-al, which is virtually devoid of thrombotic potential as well as androgenic and uterotrophic activity, could replace estrogen in the treatment of the hormone-sensitive Dunning R3327 prostatic adenocarcinoma in the male Copenhagen rat. If such were the case, the way would be open to an improved form of palliative therapy of prostatic cancer with the potential for decreased estrogenic side effects and cardiovascular complications. To this end, the R3327 tumor was transplanted (Day 0) into the flank of 10-week-old male Copenhagen rats, and treatment was begun 20 weeks later at which time the tumors reached a mean volume of 2160 cu cm. In addition to 4-androstene-3,17-dion-19-al (1 and 10 mg/day), diethylstilbestrol (33 micrograms/day) and 17 beta-estradiol (3.3 and 33 micrograms/day) were studied (daily for 60 days). At 1 mg/day, 4-androstene-3,17-dion-19-al produced a 43% inhibition of tumor growth (Day 203) while, in the 10 mg/day group, a 72% inhibition of tumor growth was measured on Day 196 (roughly equivalent to that produced by estradiol at 3.3 micrograms/day), with a 50% inhibition on Day 231. It is concluded that the tumor-inhibiting activity of 4-androstene-3,17-dion-19-al, coupled with its very low thrombotic potential, indicated that orally active analogues of this steroid may offer advantages over estrogens in the palliative treatment of prostatic cancer.

Adenocarcinoma↗