Glenn N. Taylor

The Distribution and Retention of Hexavalent 233U in the Beagle

The distribution, retention, and excretion of 233U were measured in seven beagles injected intravenously with 2.8 /zCi 233U(VI)/kg (-3 mg/dog) in citrate buffer and sacrificed at times ranging from 1 to 726 days postinjection (PI). The concentration of U in plasma decreased rapidly, and for the first 24 hr PI could be described by a triphasic exponential equation with half-times of 0.92, 46, and 315 min. The uranium in the blood at 5 min PI was present as either a protein (transferrin-albumin) or a carbonate/bicarbonate complex. Up to 60% of the injected U was excreted during the first day, most of it in the urine. Whole-body retention was 17% at 7 days, 10% at 94 days, 7.6% at 1 year, and less than 5% at 2 years PI. Except for the kidney, only a small fraction of the injected U was retained in soft tissues. At 1 day PI, the liver contained 1.1% of the injected U and its subcellular distribution was similar to that seen with Pu(IV). At 1 day PI, 7.7% of the U was found in the skeleton; this amount decreased with a biological half-life of 883 days. Initially, U was deposited nonuniformly on bone surfaces with areas of intense hot spots adjacent to areas with intermediate and low concentrations. At later times redistribution and/or diffusion of U into the bone volume produced a deposition pattern intermediate to that of 239Pu (surface) and 226Ra (volume). The heterogeneity of surface deposits persisted, and isolated segments of the trabecular bone showed intense surface deposits at times greater than 1 year PI. Twenty-two percent of the injected U was found in the kidneys at 1 day PI with high concentrations localized in the proximal tubules. The initially high concentration of U in this organ was correlated with extensive diuresis and a persistent elevation in blood urea nitrogen. Damage to proximal tubules was attributed primarily to chemical toxicity but was aggravated by simultaneous a irradiation. It is postulated that the deposition of U on trabecular endosteal surfaces will induce osteosarcoma(s) following prolonged exposure to 233U or 232U.

Nicotine and cotinine effects on 3 alpha hydroxysteroid dehydrogenase in canine prostate

We have recently observed that cigarette smoking affects plasma androgen concentrations. The effects of nicotine and cotinine, two products of cigarette smoking, on testosterone metabolism were determined. The activity of delta 4 steroid 5 alpha-reductase, which converts testosterone to 5 alpha-dihydrotestosterone (DHT) was measured in isolated dog prostate nuclei using testosterone (0-200 nM) as substrate and NADPH as cofactor. Activity of 3 alpha-hydroxysteroid dehydrogenase (HSD), which converts DHT to 3 alpha-androstanediol (3 alpha-diol) and is a reversible enzyme, was measured in isolated dog prostate microsomes with DHT (0-20 microM) as substrate and NADPH as cofactor. When microsomal fractions were incubated for 1 hour with and without nicotine (0-50 microM) and cotinine (0-100 microM), enzyme activity of HSD was significantly suppressed (p less than 0.001). The Vmax was not affected significantly (p greater than 0.60) and Km increased with increasing concentrations of nicotine and cotinine (p less than 0.05). Both nicotine and cotinine are competitive inhibitors of HSD in dog prostate microsomes with Kis of 61 and 89 microM, respectively. The apparent 5 alpha-reductase activity was unaffected by nicotine and cotinine. The inhibitors produced a marked effect on activity of HSD when used in concentrations achieved in humans who smoke cigarettes. The results suggest that nicotine and cotinine are competitive inhibitors of the HSD, an important enzyme involved in the metabolism of DHT and produce an accumulation of DHT. These products of cigarette smoking could alter androgen action in tissue such as skin and prostate.

Comparative toxicity of 226Ra, 239Pu, 241Am, 249Cf, and 252Cf in C57BL/Do black and albino mice.

Groups of C57BL/Do (black and albino) mice were injected with graded activities of 226Ra, 239Pu, 241Am, 249Cf, or 252Cf and were followed throughout life. Bone sarcoma was the principal radiation-induced end point, and the risks associated with average skeletal doses of the four transuranium radionuclides, relative to radium, were determined. The relative biological effectiveness (RBE) was calculated for each emitter by dividing its risk coefficient (bone sarcomas per 10(6) mouse-rad) by the risk coefficient for 226Ra. Combined data for males and females in both black and albino mice gave the following values +/- SD for the RBE relative to 226Ra = 1.0: 239Pu = 15.3 +/- 3.9, 241Am = 4.9 +/- 1.4, 249Cf = 5.0 +/- 1.4, and 252Cf = 2.6 +/- 0.8. About 70% of the tumors occurred in the axial skeleton, and the risk coefficient for females averaged about four times higher than for males when all five nuclides were included. The RBE of fission fragment irradiation from 252Cf for cancer induction, relative to alpha irradiation, for the combined data in all of the animals given 252Cf and 249Cf, was 0.02 +/- 0.28, in agreement with the calculated theoretical value of 0.03, based on the ratio of summed track lengths in tissue.

Increased toxicity of Na3CaDTP when given by protracted administration

Protracted administration greatly enhanced the toxicity of Na,CaDTP in beagles. Injections of 5.8 p moles/kg of Na3CaDTP, given every 5 hr, were fatal as early as 4 days after the onset of treatment. The most serious lesions were induced in the epithelial lining and related structures of the intestinal tract. Protracted administration of equal molar amounts of Na,ZnDTP was found to be much less toxic.

Eye tumors and other lesions among beagles given 90Sr or 226Ra.

Analysis of eye tumors and other eye lesions among beagles given either 90Sr or 226Ra, and among control animals, indicated that intraocular tumors in excess of the rate for our control animals were not associated with radiation from incorporated 90Sr + 90Y. It is unequivocal that eye melanomas were produced by injected 226Ra. Intraocular neoplasia, hyperplasia, hyperpigmentation, and melanosis in the eye all occurred in our control beagles given no radioactivity; however, tumor experience as currently reported for different beagle colonies may not be directly comparable because of differing rates of discovery, nonuniform nomenclature, and varying criteria for classification of lesions with their discordant interpretation by different pathologists.

Americium-241 studies in beagles.

Forty-eight adult beagles were injected with 0.00179 to 4.49 pCi 241Am/kg body mass. Retained activity in the living animals was evaluated via the 60 keV gamma-ray using a combination of total-body and partial-body counting to determine the proportion in the liver and in non-liver tissue. Soon after injection, about 50% and 40%, respectively, of the administered 241Am was deposited in the liver and non-liver tissue (mainly skeleton). In the animals injected with 0.00179-0.305 pCi/kg the liver and non-liver burdens decreased slowly each with a biological half-time of about 10 yr during the first 850 days. Two dogs injected with about 2.80 ,uCi/kg exhibited a sharp decrease in liver retention beginning about 100 days after injection accompanied by an increase in non-liver 241Am. Both showed extreme degenerative liver changes at death 401 and 448 days after injection. Similar but more slowly progressing effects were observed in the retention of 241Am by two animals injected with about 0.904pCi/kg. Excreta collections from four dogs during the first 3 weeks after injection showed that f of the excretion was urinary and that nearly 2 of the total z41Am excreted during this period appeared in the first day’s collection. Evaluation of the activity of individual bones, organs, and tissues of six animals autopsied 1-448 days after injection showed that although 241Am was distributed in many soft tissues, the liver and skeleton were the principal deposition sites; however, americium concentration in the thyroid gland was higher than in the skeleton and was higher than in any other soft tissue except the liver. Autoradiography showed that 2aArn was deposited close to the location of the functioning thyroid cells. The kidney also had a relatively high concentration of activity, selectively deposited in the glomeruli.

Plutonium- or americium-induced liver tumors and lesions in beagles

Plutonium-239 or 241Am administered intravenously in the monomeric citrate form was initially deposited in beagle livers principally in the hepatocytes and to a much lesser extent in the sinusoidal macrophages and connective tissues. The initial distribution was quite uniform throughout the hepatic parenchyma; however, at later postinjection intervals, depending on the amount of injected activity, the liver burden became increasingly more focal due to: (1) a progressive shift of the radionuclide from the hepatic epithelium to the macrophages; (2) the movement of such macrophages toward the portal or central regions of the lobule; and (3) the displacement of the older more radioactive tissue by regenerating hepatocytes, which generally have a much lower radionuclide content. The hepatic lesions produced by Pu or Am included: (1) necrosis and degenerative changes that were clinically serious or fatal in some of the animals injected with approximately 107 kBq kg-1; (2) marked structural and circulatory changes resulting from necrosis and focal hepatocyte hyperplasia; (3) a significant incidence of both benign and malignant primary liver tumors. In both Pu- and Am-treated dogs, the most frequently appearing neoplasm was the bile duct adenoma, followed by the cholangiocarcinoma. The most obvious difference between Pu- and Am-induced liver neoplasia was the greater frequency of fibrosarcomas and mast cell sarcomas in the Am-treated groups. Hepatomas were of relatively low frequency in animals with Pu or Am burdens. Although the incidence of bone neoplasia was high among the dogs in these studies, the risk of liver tumors, especially in the Am-treated animals, exceeded that of the skeleton in some of the lower dosage levels where the survival times were long. A risk coefficient of approximately 1200 fatal liver malignancies (10(4) beagle Gy)-1, derived from the dosage groups with long survival times, was calculated for combined Pu and Am animals. The prominence of the liver syndromes in beagles with burdens of Pu or Am indicates that humans with body burdens of 239Pu, 241Am, or other actinide elements may be at risk from radiation effects in the liver, including neoplasia development.

Bone cancer occurrence among beagles given 239Pu as young adults

The occurrence of skeletal malignancies has been documented among 234 young adult beagles given single intravenous injections of monomeric 239Pu citrate. Occurrence has also been documented among 132 comparable control group animals surviving the minimum latent time period of 2.79 y for radiation-induced bone cancer, who were maintained for lifespan observation. Injected amounts ranged from about 0.02-106 kBq kg-1 body mass with factors of 2 or 3 between dose levels. There were 84 radiographically apparent bone tumors in 76 plutonium-injected dogs and one tumor in a control group dog. Most of these were osteosarcomas except for seven chondrosarcomas, one liposarcoma, and one plasma cell myeloma of bone. The relationship between percent of dogs at any dose level with bone malignancy and average skeletal dose at the presumed time of tumor initiation of 1 y before death appeared to be linear below about 1.3 Gy average skeletal dose. The observed data can be approximated by the expression A = 0.76 + 75 D, where A = percent of dogs with bone cancer at any dose level, D = average skeletal dose in Gy (for doses up to 1.3 Gy) at tumor initiation, and 0.76 represents the percent tumor response in the control animals not given plutonium. Similar analysis of our corresponding data for beagles given 226Ra, excluding the two highest dose levels (approximately 100% occurrence), yielded the expression A = 0.76 + 4.7 D, where D = the average skeletal dose in Gy (for doses up to 20 Gy) at 1 y before death. The ratio of coefficients indicates the effectiveness for bone cancer induction of 239Pu relative to 226Ra, or [(75 +/- 22.5)(4.7 +/- 0.47)-1] = 16 +/- 5 for a single, brief intake of either nuclide into blood.

Removal of Pu and Am from beagles and mice by 3,4,3-LICAM(C) or 3,4,3-LICAM(S)

Decorporation of Pu and Am by tetrameric catechoylamide (CAM) ligands has been investigated in beagles and mice. Eight dogs were injected intravenously (iv) with 237 + 239Pu(IV) + 241Am(III) citrate, and 30 min later, pairs of dogs were injected iv with 30 mumole/kg of 3,4,3-LICAM(C) [N1,N5,N10,N14-tetrakis(2,3-dihydroxy-5-sulfobenzoyl)tetr aazatetradecane, tetrasodium salt], 3,4,3-LICAM(S) [N1,N5,N10,N14-tetrakis(2,3-dihydroxy-4-carboxybenzoyl)te traazatetradecane, tetrasodium salt], CaNa3-DTPA, or each of the latter two ligands. Blood was sampled, and excreta were collected for 7 days, at which time the dogs were sacrificed and nuclide retention in liver and nonliver tissue was measured. Groups of five mice were each given 238Pu(IV) or 241Am(III) citrate iv; 3 min later 30 mumole/kg of a CAM ligand was injected intraperitoneally, mice were killed at 24 hr, and separated excreta and tissues were analyzed. In the dogs, average retention at 7 days of the injected Pu and Am, respectively, was as follows: 12 and 70% after treatment with a CAM ligand alone; 30 and 20% after DTPA; 12 and 20% after LICAM(S) plus DTPA; 90 and 89% without a ligand. In the mice, mean retention of the injected Pu and Am, respectively, was as follows: 14 and 66% after treatment with LICAM(C); 21 and 54% after LICAM(S); 91 and 87% without a ligand. In both species, about 99% of net Pu excretion (excretion with ligand - excretion without ligand) promoted in 24 hr by DTPA or LICAM(S) was in the urine, whereas about 10% of net Pu excretion promoted by the less hydrophilic LICAM(C) was in feces. Delayed excretion of both Am and Pu was significant in all ligand-treated dogs. Comparison of the nuclide content of tissues of ligand-treated mice with those of mice killed 3 min after nuclide injection indicated that the CAM ligands chelated circulating Pu and Am and prevented further deposition. In addition, the CAM ligands removed much of the presumably loosely bound Pu present in liver and skeleton at the time of ligand injection. LICAM(C) was more effective in removing Pu from liver and LICAM(S) was more effective in the skeleton. Moderate to severe uremia and histological evidence of cell killing in the distal tubules of the kidney were observed in the four dogs injected once with 30 mumole/kg of LICAM(S).(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of internal emitter radiobiology in animals and humans

Investigations of radionuclide metabolism and effects in various mammalian species revealed important similarities between animals and humans and between some animal species. These include skeletal deposition of radium and radiostrontium in bone volume; deposition on bone surfaces of plutonium and other actinides; liver deposition of actinides; induction of skeletal or liver malignancies by these radionuclides; induction of tooth and jaw abnormalities; mammary cancer induction by radium in humans and in the beagle; depression of circulating cells in blood; and induction of bone fractures. There are also inter-species differences that may not have been noted if multiple species (including humans) had not been studied. Some of these are more rapid excretion of radium in humans compared with most other mammals; induction by radium of eye melanomas in animals but not humans; rapid loss of deposited plutonium from liver in many species of mice and rats but not in humans and dog; substantial sex-related differences in skeletal plutonium retention and bone sarcoma induction in mice but not in humans or dog; and induction of head sinus carcinomas by 226Ra in humans but not the beagle. Leukemia and other related neoplasms were not induced in radionuclide-injected lifespan dogs in excess of the occurrence in control animals. Much of our current understanding of skeletal biology and radionuclide behavior in mammals was derived from this and related projects. The primary goal of the Utah experiment of estimating toxicities of bone-seeking radionuclides relative to radium has been accomplished. For 226Ra = 1.0, comparative toxicities (ratios) of a single injection for bone tumor induction in beagles were about 16 ñ 5 for monomeric 239Pu (32 ñ 10 for chronic exposure), 6 ñ 0.8 for 241Am, 8.5 ñ 2.3 for 228Th, 6 ñ 3 for 249Cf, 4 ñ 2 for 252Cf, 6 ñ 2 for 224Ra (16 ñ 5 for 50 weekly injections), 2 ñ 0.5 for 228Ra, and between 0.01 n 0.01 and 1.0 n 0.5 for 90Sr, depending on the dose-rate, with the lowest dose-rates approaching a ratio of zero. Corresponding ratios in mice for 226Ra = 1.0 were 16 ñ 4 for monomeric 239Pu, 5.4 ñ 2.0 for 224Ra (16 for 50 weekly injections), 4.9 ñ 1.4 for 241Am, 5.0 ñ 1.4 for 249Cf, 2.6 ñ 0.8 for 252Cf, 4.4 ñ 1.8 for 243,244Cm and about 1.0 for 90Sr at high doses, decreasing to near zero for low doses.