Pharmacokinetics, metabolism (in vivo and in vitro), elimination and tissue distribution of 14C-parathion was studied after intravenous administration of 0.5 mg/kg to newborn, 1 week and 8 weeks old piglets. Body clearance increased from 7 ml/min./kg in newborn to 35 and 121 ml/min./kg in 1 and 8 weeks old piglets, respectively. Urinary excretion during the first 3 hr rose from 18 to 48 and 82% of the dose in newborn, 1 and 8 week old piglets. The main metabolite of parathion was p-nitrophenyl-glucuronide making up 85% of the urinary 14C excretion. About 6% was excreted as p-nitrophenyl-sulfate and only 1% as free (non-conjugated) p-nitrophenol. Unchanged parathion or paraoxon was not detectable in urine from any of the age groups. The in vitro experiments showed that biotransformation of parathion took place only when cofactors for oxidative reactions were present, indicating that oxidation is the first and necessary metabolic step and that hydrolysis does not contribute significantly to the elimination of parathion. The highest concentration of 14C 3 hr after administration was found in kidney and liver. In newborn piglets the 14C-concentration in tissues was higher than or equal to the plasma concentration. The 14C tissue/plasma ratio decreased with age for all tissues except kidney. Parathion was present in high concentrations in plasma, liver and kidney from newborn piglets, whereas the level just exceeded the detection limit in the 8 week old ones. Paraoxon was clearly detectable in plasma and liver from newborn piglets, while only traces were found in the older groups.
ABSTRACT. Tissue samples of 69 Atlantic walruses (Odobenus rosmarus rosmurus) were collected in the Thule district, North Greenland, in May-July 1975 and 1977. The mean concentration of total mercury in liver was 1.78 mg kg1 (SD = 1.54; N = 46), wet weight basis, with the mean percentage of methyl mercury being 5.5%. The mean concentration in muscle was 0.08 mg kg' (SD = 0.05; N = 58; mean age = 10.9 years; range: 1-26 years; neonates excluded). In neonates (N = 9) the mean concentration of total mercury was 0.31 mg kg' (SD = 0.45) in liver (19.9% methyl mercury) and 0.06 mg kg' (SD = 0.03) in muscle.Mean Z DDT and PCB concentrations in blubber of 28 walruses (mean age = 7.4 years; range: 0-19 years) were 0.063 mg kg' (SD = 0.080) and 0.221 mg kg' (SD = 0.207), respectively. In males the concentration of PDDT and PCB increased with age. In females there was no correlation between the concentration of PDDTand age, while there was a negative correlation between the concentration of PCB and age.
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