Shuji Ohhira

Comparative study of the metabolism of triphenyltin in hamsters and rats after a single oral treatment with triphenyltin chloride

Our previous work has shown that triphenyltin compound induces the diabetogenic effects, such as hyperglycemia and hypertriglyceridemia, on hamsters, but not on rats. In the present study, it is examined whether the species differences in the metabolic fate of triphenyltin exist for susceptibility between hamsters and rats. Triphenyltin chloride was orally dosed to hamsters and rats, and triphenyltin and its metabolites, mono- and diphenyltin, and inorganic tin, in liver, kidney, pancreas, brain, and blood were determined by gas chromatography periodically for 96 h after the treatment. Triphenyltin levels in the tissues of both species were almost maxima within 24 h after treatment. Although there were relatively high levels of triphenyltin in the tissues of hamsters dosed with triphenyltin chloride, compared with those in the rats, the proportion of metabolites to triphenyltin were lower than those in the rats. In particular, hamsters were more susceptible than rats to the pancreatic accumulations of triphenyltin and good correlation exists between the tin concentrations in the pancreas and the plasma glucose levels in triphenyltin-treated hamsters. These findings suggest that the dearylation of absorbed triphenyltin in hamsters is slower than that in rats and that triphenyltin-induced hyperglycemic action depends upon the amount of tin compounds absorbed into the pancreas. Furthermore, most of the tin compounds in the brains of both species were triphenyltin. This result shows that the metabolism of triphenyltin in the brains of both species was different from that in other tissues.

Effects of pretreatment with cytochrome P-450 inducers, especially phenobarbital on triphenyltin metabolism and toxicity in hamsters.

The effects of cytochrome P-450 (CYP) induction by phenobarbital (PB), CYP 2B, 2C, and 3A inducer in mammalians, on triphenyltin metabolism and toxicity in hamsters were studied. A single dose of 50 mg/kg of triphenyltin chloride was given by gavage to hamsters after pretreatment with or without PB for 3 days continuously at a daily dose of 80 mg/kg intraperitoneally (i.p.). Although the triphenyltin produced marked but reversible hyperglycemia and hypertriglyceridemia in PB-untreated hamsters, the pretreatment of hamsters with PB, which increased levels of CYP, suppressed the diabetogenic effects compared with PB-untreated hamsters. Furthermore, we investigated whether the mitigation of triphenyltin-induced diabetogenic toxicity by PB pretreatment is due to an alteration of triphenyltin metabolism. Triphenyltin and its metabolites in liver, kidneys, pancreas and brain were determined by gas chromatography periodically for 96 h after triphenyltin administration in both groups of hamsters. The initial triphenyltin levels in the tissues of PB-pretreated hamsters were about half of those in the tissues of PB-untreated hamsters and PB pretreatment accelerated metabolism of triphenyltin at early stage in hamsters. We also examined the other CYP 1A and 2A inducers, beta-naphthoflavone (B-NF) and 3-methylcholanthrene (MC). The PB pretreatment showed the strongest suppression of the toxicity at 24 h after the triphenyltin intubation, compared with the effects of B-NF and MC. In addition, the maximum proportion of diphenyltin to parent triphenyltin in pancreas was observed in PB-treated hamsters. These findings suggest that the induction of CYP system enzymes affects the metabolism and toxicity of triphenyltin in hamsters. Especially, based on effects of PB and other CYP inducers, PB induction has a key role in suppressing the diabetogenic action of triphenyltin, i.e. by decreasing triphenyltin accumulation in the hamsters.

Effects of pretreatment with SKF-525A on triphenyltin metabolism and toxicity in mice

The effects of cytochrome P-450 inhibition by alpha-phenyl-alpha-propylbenzeneacetic acid 2-[diethylamino]-ethyl ester hydrochloride (SKF-525A), which inhibits the activity of a number of cytochrome P-450s, on triphenyltin metabolism and toxicity in mice were studied. At 24 h after triphenyltin administration, the triphenyltin levels in the tissues of SKF-525A-pretreated mice were about three times of those in the tissues of SKF-525A-untreated mice and the ratio of metabolites to parent triphenyltin in the tissues of SKF-525A-pretreated mice was lower than those in the tissues of SKF-525A-untreated mice. These data indicate that the pretreatment of SKF-525A decelerated the triphenyltin metabolism and increased triphenyltin accumulation in the tissues of mice. Although triphenyltin did not affect plasma glucose levels of in the SKF-525A-untreated mice, the triphenyltin produced marked hyperglycemia in SKF-525A-pretreated mice. These results suggest that the inhibition of cytochrome P-450 system enzymes by SKF-525A affects the metabolism and toxicity of triphenyltin and has a key role in inducing the hyperglycemic action of triphenyltin, i.e. by increasing triphenyltin accumulation in the mice.

Gas chromatographic determination of inorganic tin in rat urine after a single oral administration of stannous chloride and mono-, di-, and triphenyltin chloride

A method is described for the determination of inorganic tin by gas chromatography with flame photometric detection. The inorganic tins, stannous and stannic, were extracted with hydrochloric acid and n-hexane-benzene in the presence of 0.05% tropolone, and both inorganic tins were pentylated to tetrapentyltin with a Grignard reagent prior to gas chromatography. The absolute limit of detection for tetrapentyltin was 3 pg as tin. The recovery of stannous chloride added to rat urine samples was 80.2 +/- 2.4% (mean +/- S.D., n = 8). The application of this method to the study of urinary excretion of inorganic tin and organotin compounds in rats following oral administration of tin compounds is presented. The urinary excretion of tin compounds was observed over a period of 96 h following administration of stannous chloride or phenyltin compounds. Most of the inorganic tin was excreted into urine within 24 h after administration of stannous chloride. In the experiments on organotin administration, the level of the excretion as total tin for monophenyltin reached a maximum ca. 0-24 h after administration, whereas the maxima for di- and triphenyltin were found after 24-48 h and 48-72 h, respectively. The predominant excretion product of these tin compounds found in urine was monophenyltin.

Simultaneous determination of butyltin and phenyltin compounds in oysters by capillary gas chromatography.

A method is described for the simultaneous determination of butyl- and phenyltin compounds in oyster samples. The organotin compounds were extracted (as chlorides) from oyster homogenates with hydrochloric acid and benzene in the presence of 0.05% tropolone. These compounds were converted into pentyl derivatives with pentyl Grignard reagent and then analysed by capillary gas chromatography with a flame photometric detector equipped with a 393-nm filter. The recoveries of six organotin compounds added to oyster samples ranged from 71 to 74%. The detection limits of butyl- and phenyltin compounds were in the 5-9 pg range as tin. We detected significant amounts of three organotin compounds (di- and tributyltin and triphenyltin) in oyster samples.

Distribution of environmental pollutants in pet animals. VI. Heavy metals in hair of house-dogs

The concentrations of cadmium, copper, lead, manganese, and zinc were determined in the hair of 40 pet dogs of both sexes. Of the heavy metals, zinc showed the highest concentration in the hair regardless of sex or color. Zinc also increased gradually with age. Cadmium and lead increased in concentration up to 7 years of age and decreased thereafter. Correlations were made among the heavy metal concentrations in the hair. Comparisons also were made with available human data. It was suggested that analysis of heavy metals in the hair of house-dogs may be valuable as a means of biological monitoring of the human heavy metal body burden. (RJC)

Comparison of sulphur-mode and tin-mode flame photometric detectors for the gas chromatographic determination of organotin compounds

A comparison of sulphur-mode (393 nm) and tin-mode (610 nm) flame photometric detectors for the gas chromatographic determination of butyl- and phenyltin compounds is described. The chromatographic peaks of the butyl- and phenyltin compounds were well separated, and high sensitivity was achieved in both modes; however, the tin-mode was more specific for tin compounds than the sulphur-mode. The absolute detection limits with the sulphur-mode and the tin-mode were 3.9-7.6 pg and 2.6-5.1 pg as tin, respectively. The application of the tin-mode gas chromatographic method to the determination of organotin compounds in fish is presented. For this application, organotins are extracted (as chloride) with hydrochloric acid and n-hexane-benzene (3:2, containing 0.05% tropolone) and the extracts are pentylated by a Grignard reagent prior to gas chromatography. The absolute recoveries of butyl- and phenyltin compounds added to fish samples ranged from 68.5 to 84.4% (the coefficients of variation were less than 6.6% for all substances, n = 8). Significant amounts of three organotin compounds (di- and tributyltin and triphenyltin) in fish samples were detected by this method. This technique may have application for other organotin compounds and the monitoring of butyl- and phenyltin compounds in the environment.