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PubMed1997

Effects of hyperthyroidism and radioactive iodine given to ablate the thyroid on the composition of whole stimulated saliva.

OBJECTIVE: For many years there has been speculation about possible damage to the salivary glands following administration of ablative doses of radioactive iodine for treatment of hyperthyroidism. We have investigated the changes that occur in the composition of saliva in hyperthyroidism and after the administration of an ablative dose of radioactive iodine to hyperthyroid subjects. DESIGN: The study consisted of two parts: first, a comparison of a group of hyperthyroid patients with a group of normal subjects with regard to the concentration or activity of 10 constituents of saliva; second, measurement of those constituents 3-42 weeks after administration of 370 MBq of radioactive iodine to a group of hyperthyroid subjects. PATIENTS: Saliva specimens from 38 untreated out-patients with hyperthyroidism due to Graves' disease or toxic nodular goitre were studied to evaluate the effects of hyperthyroidism and the results were compared with a group of 93 normal subjects. Seventy-one samples of saliva from 26 patients with persistent hyperthyroidism were collected and analysed 3-42 weeks after radioactive iodine administration. MEASUREMENTS: The flow rate; the concentrations of total protein, iodine, calcium, urate, phosphate, potassium and immunoglobulin A; and the activities of N-acetylglucosaminidase, lysozyme and lactate dehydrogenase were measured. RESULTS: In hyperthyroidism the salivary flow rate and the concentrations of urate and potassium were significantly (P < 0.05) increased and the concentrations of total protein, calcium and lactate dehydrogenase activity significantly decreased compared to the control group. After radioactive iodine was administered, significant positive trends were observed in the concentrations of total protein, N-acetylglucosaminidase and immunoglobulin A. These trends were independent of the free T3 levels obtained from the same specimens. CONCLUSIONS: Hyperthyroidism leads to a number of changes in salivary composition. For most of the salivary components measured no significant changes were observed 3-42 weeks after administration of 370 MBq of radioactive iodine to patients with persistent hyperthyroidism. The relatively small positive trends in the concentrations of total protein, N-acetylglucosamidase activity and immunoglobulin A may have been due either to changes in thyroid status or to the effects of radiation on the salivary glands, or both.

Acetylglucosaminidase↗
PubMed1984

Studies on acrosome labelling of mammalian spermatozoa by radioactive sugars.

The localization of glycoprotein synthesis and storage was studied during acrosome formation in guinea-pig using fine-structure autoradiography after (3H)-fucose incorporation. Three days after (3H)-fucose injection, labelling in spermatids was concentrated in the matrix of developing acrosomes, and it was evident that the fucosylation of acrosomal glycoproteins largely overshadowed the fucosylation of other spermatid glycoproteins. Acrosin labelling and its quantitative relation to labelling of other glycoproteins was examined in mature rabbit spermatozoa after incorporation of (14C)-fucose or (14C)-glucosamine during spermatogenesis. Cauda epididymis spermatozoa recovered 21 days after intratesticular application of (14C)-fucose or (14C)-glucosamine were analysed for acrosin specific labelling after acid extraction and gel filtration. In all the material examined, radioactivity was detected in the proacrosine fractions; radioactivity in purified proacrosin amounted to at least 2% of the total radioactivity in the epididymal sperm population. In addition to the peak with radioactive proacrosin, another radioactive peak in (14C)-glucosamine-labelled material was attributed to a glycoprotein intraacrosomal inhibitor of acrosin. It is concluded that (pro)acrosin (acrosin-inhibitor) complexes seem to contribute significantly to acrosomal glycoprotein labelling by radioactive sugars and that the distribution of these complexes may at least correspond to their cytochemically detectable component, acrosin. The superposition of the distribution of acrosin and of other acrosomal glycoproteins during acrosome reaction can be explained by the fact that the dispersal of most of the acrosomal content is linked to proacrosin activation.

Acrosin↗
PubMed2001

Clinical and angiographical follow-up after implantation of a 6--12 microCi radioactive stent in patients with coronary artery disease.

AIMS: This study is the contribution by the Thoraxcenter, Rotterdam, to the European(32)P Dose Response Trial, a non-randomized multicentre trial to evaluate the safety and efficacy of the radioactive Isostent in patients with single coronary artery disease. METHODS AND RESULTS: The radioactivity of the stent at implantation was 6--12 microCi. All patients received aspirin indefinitely and either ticlopidine or clopidogrel for 3 months. Quantitative coronary angiography measurements of both the stent area and the target lesion (stent area and up to 5 mm proximal and distal to the stent edges) were performed pre- and post-procedure and at the 5-month follow-up. Forty-two radioactive stents were implanted in 40 patients. Treated vessels were the left anterior descending coronary artery (n=20), right coronary artery (n=10) or left circumflex artery (n=10). Eight patients received additional non-radioactive stents. Lesion length measured 10+/-3 mm with a reference diameter of 3.07+/-0.69 mm. Minimal lumen diameter increased from 0.98+/-0.53 mm pre-procedure to 2.29+/-0.52 mm (target lesion) and 2.57+/-0.44 mm (stent area) post-procedure. There was one procedural non-Q wave myocardial infarction, due to transient thrombotic closure. Thirty-six patients returned for angiographical follow-up. Two patients had a total occlusion proximal to the radioactive stent. Of the patent vessels, none had in-stent restenosis. Edge restenosis was observed in 44%, occurring predominantly at the proximal edge. Target lesion revascularization was performed in 10 patients and target vessel revascularization in one patient. No additional clinical end-points occurred during follow-up. The minimal lumen diameter at follow-up averaged 1.66+/-0.71 mm (target lesion) and 2.12+/-0.72 (stent area); therefore late loss was 0.63+/-0.69 (target lesion) and 0.46+/-0.76 (stent area), resulting in a late loss index of 0.65+/-1.15 (target lesion) and 0.30+/-0.53 (stent area). CONCLUSION: These results indicate that the use of radioactive stents is safe and feasible, however, the high incidence of edge restenosis makes this technique currently clinically non-applicable.

Adult↗
PubMed1979

Cellular interaction between fixed and living cells. Transfer of radioactive materials from living cells to fixed cells.

Transfer of radioactive materials to fixed cells from an overlying layer of living cells has been examined to determine whether fixed cells can act as acceptors of glycosyltransferases of living cells. After the incubation of living cells were removed by EDTA treatment, and the radioactivity associated with the fixed cells was determined. Lipids, proteins and carbohydrates were found to be transfered from the living cells to the fixed cells. The amount of radioactivity transferred to the fixed cells was dependent on the number of both fixed and living cells and increased with the time of incubation. When fixed cells were treated with chloroform-methanol before the addition of living cells, the transfer of both lipids and proteins to the fixed cells decreased drastically, but only a slight decrease incarbohydrate transfer was observed. Most of the radioactive materials transferred from living cells labeled with glucosamine or fucose to chloroform-methanol-treated fixed cells were solubilized by trypsin but not by the detergents tested. Approximately 55% of the materials transferred from the cells labeled with glucosamine could be solubilized by hyaluronidase and chondroitinase, and the rest was solubilized by neuraminidase and a glycosidase mixture. The treatment of chloroform-methanol-extracted fixed cells with trypsin caused a significant decrease in the transfer from cells labeled with glucosamine. When nucleotide sugars were used as the radioactive precursor, no significant amount of radioactivity was transferred to the fixed cells.

Autoradiography↗
PubMed1993

Binding, internalization and excretion of TGF alpha-dextran associated radioactivity in cultured human glioma cells.

Conjugates based on transforming growth factor alpha, TGF alpha, or epidermal growth factor, EGF, are candidates for targeted radiotherapy against EGF-receptor rich tumours such as gliomas or squamous carcinomas. In this study, binding, internalization and excretion of radiolabelled TGF alpha and TGF alpha-dextran conjugates was analysed in an EGF-receptor rich human glioma cell line. The binding of 125I-TGF alpha was EGF-receptor specific and the binding pattern was similar to that of 125I-EGF. The TGF alpha-dextran conjugate also bound specifically but gave maximum binding for a longer time during continuous incubation compared to when only TGF alpha was used. The excretion pattern of internalized radioactivity was somewhat slower for 125I-TGF alpha-dextran, with 125I-labelling on the TGF alpha part, as compared to 125I-TGF alpha although most of the radioactivity in both cases was excreted within 4 hours. The fate of the dextran part of the conjugate, as followed by means of 125I-labelling of the dextran, was different since all radioactivity in that case remained cell-associated for at least up to 22 hours. Furthermore, by comparison with previously published results, it was seen that the radioactivity delivered through the TGF alpha part of TGF alpha-dextran was retained for a shorter period of time by the cells than when delivered by EGF in EGF-dextran conjugates. However, when the radioactivity was delivered by the dextran part of the conjugates, the radioactivity seemed to be retained equally well or even better when TGF alpha-dextran was applied. It is concluded that TGF alpha-dextran, as well as EGF-dextran, have interesting properties for targeting against EGF-receptors and that the dextran part is well retained in the cells and therefore might be a suitable carrier for toxic agents such as radionuclides. It is of high interest to continue with toxicological and pharmacological in vivo studies of the conjugates.

Binding Sites↗
PubMed1999

FISH analysis of 1cen-1q12 breakage, chromosome 1 numerical abnormalities and centromeric content of micronuclei in buccal cells from thyroid cancer and hyperthyroidism patients treated with radioactive iodine.

One of the health consequences of the Chernobyl nuclear power plant accident was a radioactive iodine-related increase in the incidence of thyroid cancer in exposed children. This radioisotope is used in the treatment of thyroid cancer and hyperthyroidism patients providing a convenient opportunity to study cytogenetic damage induced by known doses of radioactive iodine in treated patients. We used pancentromeric FISH on micronuclei and chromosome 1 tandem labelling FISH to monitor overall chromosome breakage and loss, 1q12 breakage and decondensation and chromosome 1 numerical abnormalities in buccal cells from 31 radioactive iodine-exposed hyperthyroidism and thyroid cancer patients. The overall outcome of the study, with 250,000 buccal cells analysed, is that there was no radioactive iodine-related increase in the frequency of micronuclei, 1q12 breakage, 1q12 decondensation or chromosome 1 numerical abnormalities. In addition, neither age nor gender, health status nor radioactive iodine dose modulated the frequency of the above cytogenetic end points. Although several uncertainties of these emerging molecular cytogenetic methodologies will require further experimentation, we conclude that, at the reported exposure levels, radioactive iodine did not induce detectable chromosome damage in buccal cells from treated patients.

Adult↗
PubMed2004

PBPK model for radioactive iodide and perchlorate kinetics and perchlorate-induced inhibition of iodide uptake in humans.

Detection of perchlorate (ClO4-) in several drinking water sources across the U.S. has lead to public concern over health effects from chronic low-level exposures. Perchlorate inhibits thyroid iodide (I-) uptake at the sodium (Na+)-iodide (I-) symporter (NIS), thereby disrupting the initial stage of thyroid hormone synthesis. A physiologically based pharmacokinetic (PBPK) model was developed to describe the kinetics and distribution of both radioactive I- and cold ClO4- in healthy adult humans and simulates the subsequent inhibition of thyroid uptake of radioactive I- by ClO4-. The model successfully predicts the measured levels of serum and urinary ClO4- from drinking water exposures, ranging from 0.007 to 12 mg ClO4-/kg/day, as well as the subsequent inhibition of thyroid 131I- uptake. Thyroid iodine, as well as total, free, and protein-bound radioactive I- in serum from various tracer studies, are also successfully simulated. This model's parameters, in conjunction with corresponding model parameters established for the male, gestational, and lactating rat, can be used to estimate parameters in a pregnant or lactating human, that have not been or cannot be easily measured to extrapolate dose metrics and correlate observed effects in perchlorate toxicity studies to other human life stages. For example, by applying the adult male rat:adult human ratios of model parameters to those parameters established for the gestational and lactating rat, we can derive a reasonable estimate of corresponding parameters for a gestating or lactating human female. Although thyroid hormones and their regulatory feedback are not incorporated in the model structure, the model's successful prediction of free and bound radioactive I- and perchlorate's interaction with free radioactive I- provide a basis for extending the structure to address the complex hypothalamic-pituitary-thyroid feedback system. In this paper, bound radioactive I- refers to I- incorporated into thyroid hormones or iodinated proteins, which may or may not be bound to plasma proteins.

Female↗
PubMed1985

Natural radioactivity of Australian building materials, industrial wastes and by-products.

The natural radioactivity due to the presence of 226Ra, 232Th and 40K in conventional raw materials and some solid industrial wastes and by-products which are being used or have a potential for use in the building and ceramic industries in Australia has been measured by gamma-ray spectrometry. The majority of materials examined in this work showed fairly low levels of radioactivity. Some samples of red mud, phosphogypsum, zircon products and fly ash did show higher levels of radioactivity than would be acceptable on the basis of a criterion formula for gamma-ray activity suggested for use in some OECD countries. But this higher level of radioactivity should not pose an environmental health problem when these materials constitute a relatively small portion of the materials used in a normal building. The present work has also shown that the radioactivity levels of some of the materials can be reduced through the removal of fines by sieving, as the fines seem to contain a higher concentration of radioactive nuclides.

Australia↗
PubMed2006

Applied radioactivity in radiation synovectomy with [188Re]rhenium sulfide suspension.

BACKGROUND: Early experience demonstrated absorbed dose in radiation synovectomy is about 100 Gy. For reaching this dose, the applied radioactivity should be calculated. METHOD: Twenty-nine synovitic models of rabbit were treated by intra-articular injection of [(188)Re]rhenium sulfide and histological changes of synovium and cartilage were examined. The applied radioactivity was calculated by method of absorbed dose factor. In clinical, eleven haemophilic patients with haemarthrosis were performed radiation synovectomy with treated [(188)Re]rhenium sulfide. The synovial thickness was evaluated by MR and its value was used to calculate the applied radioactivity. After radiation synovectomy, all patients were followed up by synovial thickness, regional inflammation, and clinical course including bleeding frequency. RESULTS: In rabbit models, the synovitic membrane can be eliminated by calculated radioactivity as planed without damaging the joint cartilage. In patients study, all patients exhibited significant reductions in synovial thickness and inflammation after radiation synovectomy with the planed radioactivities of [(188)Re]rhenium sulfide. Post-procedure bleeding frequency reduction in excellent and good reached to 63.6% by 18 months. In the cases of joint bleeding, the need for antihaemophilic factor treatment decreased immensely. Most of the recurrent episodes of bleeding were mild, subsiding with local means. CONCLUSION: The applied radioactivity in radiation synovectomy could be calculated according to thickness of inflamed synovium. Further study including comparison therapeutic results from calculated individual activities with results from fixed activities and long-term follow-up is warranted.

Adult↗
PubMed1973

Absorption and distribution of high specific radioactivity 2-C-abscisic Acid in cotton seedlings.

High specific radioactivity (26.3 mc/mmole) racemic 2-(14)C-abscisic acid was synthesized. An aliquot of abscisic acid, 1.2 x 10(-4)m in aqueous methanolic solution, was applied to the surface of either a cotyledon or the first true leaf of 8- to 32-day-old cotton seedlings (Gossypium hirsutum L.). After various intervals (6-192 hours), the seedlings were processed for autoradiography, counting, and identification of the radioactivity. After 6 hours, radioactivity was observed moving basipetally out of the treated leaf toward the roots. Four days later, radioactivity could be detected throughout the whole seedling. After 8 days, 10% of the recovered radioactivity was found in the roots, and 80% remained in the treated leaf blade. Neither leaf type nor age had any effect on the abscisic acid movement or pattern of distribution. Isolated radioactivity from the roots was identified as abscisic acid, based on comparison with an authentic standard by thin layer chromatography, gas-liquid chromatography, or gas-liquid chromatography-mass spectrometry.

Journal Article↗
PubMed2006

Covalent binding of radioactivity from [14C]rofecoxib, but not [14C]celecoxib or [14C]CS-706, to the arterial elastin of rats.

Rofecoxib is a cyclooxygenase-2 (COX-2) inhibitor that has been withdrawn from the market because of an increased risk of cardiovascular (CV) events. With a special focus on the arteries, the distribution profiles of radioactivity in rats orally administered [14C]rofecoxib were investigated in comparison with two other COX-2 inhibitors, [14C]celecoxib and [14C]CS-706 (2-(4-ethoxyphenyl)-4-methyl 1-(4-sulfamoylphenyl)-1H-pyrrole), a novel selective COX-2 inhibitor. Whole-body autoradioluminography and quantitative determination of the tissue concentrations showed that considerable radioactivity is retained by and accumulated in the thoracic aorta of rats after oral administration of [14C]rofecoxib, but not [14C]celecoxib or [14C]CS-706. Acid, organic solvent, and proteolytic enzyme treatments of aorta retaining high levels of radioactivity from [14C]rofecoxib demonstrated that most of the radioactivity is covalently bound to elastin. In agreement with this result, the radioactivity was found to be highly localized on the elastic fibers in the aorta by microautoradiography. The retention of radioactivity on the elastic fibers was also observed in the aortic arch and the coronary artery. These findings indicate that [14C]rofecoxib and/or its metabolite(s) are covalently bound to elastin in the arteries. These data are consistent with the suggestion of modified arterial elasticity leading to an increased risk of CV events after long-term treatment with rofecoxib.

Animals↗
PubMed1976

Synthesis of biologically active spin-labelled radioactive cytidine diphosphodiglyceride, a novel probe for biological membranes.

A versatile synthesis of spin-labelled radioactive cytidine diphospho-sn-1,2-diacylglycerol (CDP-diglyceride) has been developed based on the combination of the enzymatic acylation of radioactive sn-glycero-3-phosphate with 12-doxyl stearic acid and the chemical conversion of the thus obtained spin-labelled radioactive phosphatidic acid with cytidine monophosphomorpholi-date into spin-labelled radioactive CDP-diglyceride. The method for the isolation and purification of the latter compound was described. This obtained CDP-[2-3H]diglyceride contained 10% of fatty acids of paramagnetic nature, presumably present as a covalently bound 12-doxyl stearic acid esters. The biological activity was tested by using the synthesized compound as a substrate in the mitochondrial biosynthesis of phosphatidylglycerol. It was found that spin-labelled CDP-[2-3H]diglyceride prepared as described can be converted in the presence of sn-[2-14C]-glycero-3-phosphate into a spin-labelled [2-3H, 2'-14C]phosphatidylglycerol with isolated rat liver mitochondria, establishing therefore that the site of its utilization is identical with the site of phosphatidylglycerol synthesis in isolated mitochondria, i.e. inner mitochondrial membrane. Results described demonstrate that the synthesized spin-labelled CDP-diglyceride can be used as a specific probe for the spin- and radioactive covalent labelling of polyglycerophosphatides of mitochondrial membranes. Some implications and further possibilities in the study of biological membranes using the spin-labelled radioactive CDP-diglyceride are discussed.

Animals↗
PubMed2003

Assessment of the tissue distribution of transplanted human endothelial progenitor cells by radioactive labeling.

BACKGROUND: Transplantation of endothelial progenitor cells (EPCs) improves vascularization and left ventricular function after experimental myocardial ischemia. However, tissue distribution of transplanted EPCs has not yet been monitored in living animals. Therefore, we tested whether radioactive labeling allows us to detect injected EPCs. METHODS AND RESULTS: Human EPCs were isolated from peripheral blood, characterized by expression of endothelial marker proteins, and radioactively labeled with [111In]indium oxine. EPCs (106) were injected in athymic nude rats 24 hours after myocardial infarction (n=8) or sham operation (n=8). Scintigraphic images were acquired after 1, 24, 48, and 96 hours after EPC injection. Animals were then killed, and specific radioactivity was measured in different tissues. At 24 to 96 hours after intravenous injection of EPCs, approximately 70% of the radioactivity was localized in the spleen and liver, with only approximately 1% of the radioactivity identified in the heart of sham-operated animals. After myocardial infarction, the heart-to-muscle radioactivity ratio increased significantly, from 1.02+/-0.19 in sham-operated animals to 2.03+/-0.37 after intravenous administration of EPCs. Injection of EPCs into the left ventricular cavity increased this ratio profoundly, from 2.69+/-1.54 in sham-operated animals to 4.70+/-1.55 (P<0.05) in rats with myocardial infarction. Immunostaining of cryosections from infarcted hearts confirmed that EPCs homed predominantly to the infarct border zone. CONCLUSIONS: Although only a small proportion of radiolabeled EPCs are detected in nonischemic myocardium, myocardial infarction increases homing of transplanted EPCs in vivo profoundly. Radiolabeling might eventually provide an useful tool for monitoring the fate of transplanted progenitor cells and for clinical cell therapy.

Animals↗
PubMed1999

Dose-response effects of 32P radioactive stents in an atherosclerotic porcine coronary model.

BACKGROUND: Experimental studies have demonstrated that 32P radioactive stents reduce neointimal formation at 28 days in porcine iliac and coronary arteries. Our objective was to determine the long-term dose-response effects of 1.0- to 12.0-microCi 32P radioactive stents in a porcine atherosclerotic coronary model. METHODS AND RESULTS: Control (n=19) and 1.0- to 12.0-microCi 32P radioactive (n=43) stents (total, n=62) were implanted in the coronary arteries of 31 miniature swine at 28 days after creation of a fibrocellular plaque by overstretch balloon injury and cholesterol feeding. Angiography and histomorphometry were performed at 6 months. Stent thrombosis occurred in 3 radioactive (7.7%) and no control stents (P=0.54). On histology, the mean neointimal area and the percent in-stent stenosis correlated positively with increasing stent activity (r=0.64, P<0.001). The mean neointimal area (mm2) for the stents with >/=3.0 microCi 32P (3.57+/-1.21) was significantly greater than that for the nonradioactive stents (1.78+/-0.68, P<0.0001). The neointima of the stents with >/=3.0 microCi 32P was composed of smooth muscle cells, matrix proteoglycans, calcification, foam cells, and cholesterol clefts. CONCLUSIONS: Continuous low-dose-rate irradiation delivered by high-activity (32)P radioactive stents promotes the formation of an "atheromatous" neointima after 6 months in this experimental model. These data may be useful for predicting late tissue responses to radioactive stents in human coronary arteries.

Animals↗
PubMed2000

Positive geometric vascular remodeling is seen after catheter-based radiation followed by conventional stent implantation but not after radioactive stent implantation.

BACKGROUND: Recent reports demonstrate that intracoronary radiation affects not only neointimal formation but also vascular remodeling. Radioactive stents and catheter-based techniques deliver radiation in different ways, suggesting that different patterns of remodeling after each technique may be expected. METHODS AND RESULTS: We analyzed remodeling in 18 patients after conventional stent implantation, 16 patients after low-activity radioactive stent implantation, 16 patients after higher activity radioactive stent implantation, and, finally, 17 patients who underwent catheter-based radiation followed by conventional stent implantation. Intravascular ultrasound with 3D reconstruction was used after stent implantation and at the 6-month follow-up to assess remodeling within the stent margins and at its edges. Preprocedural characteristics were similar between groups. In-stent neointimal hyperplasia (NIH) was inhibited by high-activity radioactive stent implantation (NIH 9.0 mm(3)) and by catheter-based radiation followed by conventional stent implantation (NIH 6.9 mm(3)) compared with low-activity radioactive stent implantation (NIH 21.2 mm(3)) and conventional stent implantation (NIH 20.8 mm(3)) (P:=0.008). No difference in plaque or total vessel volume was seen behind the stent in the conventional, low-activity, or high-activity stent implantation groups. However, significant increases in plaque behind the stent (15%) and in total vessel volume (8%) were seen in the group that underwent catheter-based radiation followed by conventional stent implantation. All 4 groups demonstrated significant late lumen loss at the stent edges; however, edge restenosis was seen only in the group subjected to high-activity stent implantation and appeared to be due to an increase in plaque and, to a lesser degree, to negative remodeling. CONCLUSIONS: Distinct differences in the patterns of remodeling exist between conventional, radioactive, and catheter-based radiotherapy with stenting.

Adult↗
PubMed2003

Assessment of radioactive residues arising from radiolabel instability in a multiple dose tissue distribution study in rats.

Our study objectives were: To quantitatively determine the effect of radiolabel instability on terminal phase radioactive tissue residues in a multiple dose tissue distribution study. To quantitatively compare tissue residue artifacts (non drug-related radioactivity) from two chemically-distinct radiolabel locations. To conduct a definitive multiple dose tissue distribution study using the better of the two radiolabeled compounds. We compared the excretion and tissue distribution in rats of [(14)C]linezolid, radiolabeled in two different locations, after 7 consecutive once daily [(14)C] oral doses. The radiolabels were in the acetamide (two carbon) and oxazolidinone (isolated carbon) functional groups. Terminal phase tissue residue and excretion data were compared to data from rats dosed orally with [(14)C]sodium acetate. Drug-related radioactivity was excreted rapidly over 24 h. After a single dose, the acetamide and oxazolidinone radiolabel sites both gave 3% of dose as exhaled (14)CO(2). After 7 daily [(14)C] oral doses, terminal phase radioactive tissue residues were higher from the acetamide radiolabel, relative to the oxazolidinone radiolabel, and were primarily not drug-related. In the definitive tissue distribution study, low concentrations of drug-related radioactivity in skin and thyroid were observed. We conclude that although small amounts of radiolabel instability do not significantly affect single dose tissue radioactivity C(max) and AUC, artifacts arising from radiolabel instability can prolong the apparent terminal phase half life and complicate study data interpretation. When possible, it is always preferable to use a completely stable radiolabel site.

Acetamides↗
PubMed2003

Relationship between orally administered dose, surface emission rate for gamma radiation, and urine radioactivity in radioiodine-treated hyperthyroid cats.

OBJECTIVE: To determine the relationship between surface emission rate of gamma radiation and urine concentration of I131 (urine radioactivity) during the period 7 to 21 days after oral or SC administration of I131 to hyperthyroid cats. ANIMALS: 47 hyperthyroid cats administered I131 PO and 24 hyperthyroid cats administered I131 SC. PROCEDURE: A dose of I131 (1.78 to 2.04 X 10(2) MBq [4.8 to 5.5 mCi]) was administered orally. Surface emission at the skin adjacent to the thyroid gland on days 7, 10, 14, 18, and 21 and number of counts/30 s in a urine sample (1 mL, obtained via cystocentesis) on days 7, 14, and 21 after oral administration were measured. Effective half-life (T1/2E) was derived for each point. Surface emission thresholds for maximum urine radioactivity values were established. A dose of I131 (1.48 X 10(2) MBq [4.0 mCi]) was administered SC. Urine radioactivity and surface emission rates for SC administration were compared with values for oral administration. RESULTS: The T1/2E for surface emissions and urine radioactivity progressively increased toward values for physical T1/2 over time. The T1/2E for surface emissions was 2.19 to 4.70 days, and T1/2E for urine radioactivity was 2.16 to 3.67 days. Surface emission rates had a clinically useful threshold relationship to maximum urine concentrations of I131. CONCLUSIONS AND CLINICAL RELEVANCE: Surface emission rates for cats administered I131 appeared useful in determining upper limits (threshold) of urine radioactivity and are a valid method to assess the time at which cats can be discharged after I131 administration.

Animals↗
PubMed1975

Characterization of metabolites in domestic sow urine after intravenous administration of radioactive estrogen and corticosteroids.

We measured distribution of radioactivity among urinary metabolites excreted in nonpregnant and ovariectomized sows after intravenous injection of radionuclides (14carbon) labeled estrone, estradiol-17beta, cortisol, and corticosterone. Treatment with an enzyme preparation (Glusulase) containing both beta-glucuronidase and sulfatase activity, rendered extractable over 95% of the radioactivity recovered from urine with diethyl ether (estrogens) and ethyl acetate (corticoids). Only an additional 1 to 4% of the radioactivity was extracted following solvolysis of the aqueous residue remaining after enzyme hydrolysis and extraction. Radioactivity in nonpregnant sow urine was predominantly in the estrone fraction following injection of either estrone or estradiol-17beta. Moreover, the principal metabolite was estrone monoglucuronide. Only traces of estradiol-17beta and an estriol-like compound were detected. Two other isolates contained radioactivity. One compound probably was 2-methoxyestrone, but structure of the other compound (X1) could not be established. The principal urinary metabolites from injection of cortisol corresponded to chromatographic properties of tetrahydrocortisol and tetrahydrocortisone. Both metabolites were low in urine following injection of corticosterone. The major urinary metabolites from corticosterone injection corresponded to chromatographic properties of tetrahydrocorticosterone and corticosterone. Considerable radioactivity from injection of both corticoids was isolated in the cortol, cortolone, and 11-ketoetiocholanolone - 11beta-hydroxyetiocholanolone areas of chromatograms. The data for corticoids agree with similar data for the human being and cow.

11-Hydroxycorticosteroids↗