Effect of cadmium on hepatic metallothionein level in early development of the rat

Abstract

The induction of hepatic metallothionein (MT) was investigated 24 hr after an intraperitoneal injection of 0.75 mg/kg Cd as CdCl 2 · H 2O in rats of 7, 14, 21, and 90 days. Metallothionein in liver cytosolic fractions collected on Sephadex G-75 was characterized in terms of sulfhydryl, total protein, Cd, and Zn contents. Most of the cytosolic Cd was associated with MT and the concentration of Cd was equal in the different age groups. The higher contents of sulfhydryl, protein, and Zn both in control as well as in Cd-injected rats of 7 and 14 days than in those of 21 and 90 days indicate the presence of more native Zn-thionein in immature pups. However, the increase in sulfhydryl and protein contents showed more prominent induction of MT in Cd-exposed animals of 21 and 90 days than in those of 7 and 14 days. The concentration of Cd was highest in liver followed by the other tissues. While hepatic accumulation of Cd was similar in all age groups, the renal accumulation increased significantly with age. The intestine and spleen of immature pups concentrated more Cd than those of mature animals. The accumulation of the metal did not differ significantly in heart and brain of the animals among the four groups.