Depression of serum cholinesterase activity by cadmium

Two serum enzymes which originate from the liver under different circumstances were examined as potential biological indicators in serum for cadmium toxicity. The first of those is an enzyme that leaks from damaged liver cells. The second is an enzyme that is secreted by the normal functioning liver. Cadmium chloride was injected s.c. into male and female rats of the Wistar strain (8, 15 and 22 weeks old), at doses of 1.0, 1.5 and 2.0 mg Cd/kg body weight (in total 18 groups). Cholinesterase (CHE; EC 3.1.1.8) activity in serum was found to decrease with time after the administration of a single injection of cadmium chloride and, in all experimental groups, was significantly lower than the control values on day 2 after the injection. Glutamic pyruvic transaminase (GPT; EC 2.6.1.2) activity in serum, however, increased only in the oldest group of males receiving the high dose levels of cadmium. A time-course experiment in which male and female rats 15 weeks of age were administered 1.5 mg Cd/kg body weight showed that the serum CHE activity started to decrease on day 1 after the injection, attained the lowest level on days 2 and 3, and then recovered almost to control levels on day 5. On the other hand, the GPT activity remained at or less than control values throughout the experimental period. The results indicate that CHE activity in serum is a sensitive biological indicator for cadmium toxicity.