When doses of 0.3 to 2 mg/kg of mercuric chloride were intravenously administered to rats of the JCL-SD strain, acute renal tubular necrosis was produced in the straight portion of the proximal tubules with a pronounced sex difference, the male being more susceptible. Necrosis was inhibited by castration of male rats and promoted by testosterone pretreatment. When 0.15 mg of mercury per rat was injected to adult rats, females showed higher levels of mercury in the whole kidney, outer cortex and inner cortex. Castration of male rats caused elevated renal levels of mercury and pretreatment with testosterone of females lowered the levels. Renal levels of sulfhydryl groups were higher in female than male rats and castrated male rats showed elevated renal levels. The sex difference in the l evels of sulfhydryl groups seems to be one factor which causes different susceptibility to mercury between males and females.
The clearance of intravenously injected colloidal carbon from the peripheral blood was investigated in mice, rats, rabbits and dogs. The blood clearance of carbon was more rapid in the young than in the old for all the species examined. A biphasic clearance curve was observed in the dogs of all age groups tested, and in the rabbits of 8 and 16 weeks old. The rate of colloidal carbon clearance was slower in the rabbits than in other three species.
I. V. self-administration of cinepazide by rats and the preference of the animals for this drug were studied; and the following were found: 1. I. V. self-administration of cinepazide to rats at dosages of 4, 15, 30, and 60 mg/kg/injection for 7 consecutive days resulted in no self-administration by the animals of the drug far beyond the operant level. 2. Rats undertook the self-administration of cocaine at 1 mg/kg/injection continuously, unlike that of saline or cinepazide. 3. Cross application of cinepazide at dosages of 4, 15, 30 and 60 mg/kg/injection to rats on i. v. self-administration of cocaine failed to substitute itself for the latter. These findings suggested that cinepazide was not a positive reinforcer. 4. Rats exhibited preference for morphine, codeine and pethidine but not for cinepazide. 5. The rats exhibiting preference for morphine also exhibited preference for codeine and pethidine in cross choice trials with these drugs but not for cinepazide in the cross choice trial with this drug. The findings in 4 and 5 suggested that rats showed no preference for cinepazide and that cinepazide failed to maintain the rats' preference for morphine.
Rabbits were exposed to elemental mercury (Hg°) vapor, methyl mercury (MeHg) and HgCl2 respectively, and the relationship of mercury concentration in brain to that in blood or cerebrospinal fluid (CSF) was investigated after the termination of exposure. At one day post-exposure, the ratio of mercury concentration in brain (μg Hg/g) to that in blood (μg Hg/g) was approximately 10.0 in Hg° vapor, 0.6 in HgCl2 and 3.0 in MeHg. The ratio for Hg° vapor was about 10 times higher than that for HgCl2. In rabbits exposed to Hg° vapor, the ratios of mercury concentration in blood to brain or CSF to brain at 1 day and 20 days after the termination of exposure were compared. The blood to brain ratio showed a decrease to about 1/10 after 20 days, and the CSF to brain ratio, a decrease of about 1/2. The results obtained seems to suggest that mercury is eliminated from the blood and CSF more rapidly than from the brain. In the case of rabbits administrated MeHg, the ratio of mercury concentration in blood to that in brain was almost unchanged at both 1 day and 20 days after the termination of exposure. There did not seem to be any differences in the rates of elimination from blood and brain. The elimination of mercury from CSF was more rapid than from brain because the ratio between the mercury concentration of CSF to that of brain showed a decrease to about 1/3 after 20 days.