Sex and restraint stress differences in rat metallothionein and Zn levels.

Sex differences in serum and liver metallothionein (MT) levels were studied in adult male and female rats. Whereas it was found that female rats had higher hepatic MT levels than male rats in basal, unstressed conditions, no significant differences were found in serum MT levels. Restraint stress increased both serum and liver MT in both sexes. The increase in serum MT was greater in male than in female rats, whereas no significant differences between sexes were found in liver MT content after restraint stress. It is suggested that MT regulation might be sex-dependent and that MT might play some extrahepatic function during stress.