NATIVE METALLOTHIONEIN LEVELS IN RAT HEPATIC CYTOSOL DURING PERINATAL-DEVELOPMENT

The development of hepatic metallothionein has been examined in the Sprague-Dawley rat at term and at 7, 14, 21, 28, and 35 days after birth. Using gel-filtration techniques, metallothionein levels were found to be relatively high in the term fetus and 7-day-old neonate but then to decrease markedly to nondetectable levels by Day 28. Significant amounts of endogenous zinc were associated with metallothionein, the bulk of which could be displaced by in vitro exposure to cadmium chloride. In the presence of saturating levels of cadmium chloride, 20% of the endogenous zinc was resistant to displacement, suggesting that the binding affinity of endogenous zinc for sites on metallothionein might not be homogeneous. Experimental results indicate that metallothionein might serve as a regulator of hepatic zinc during the perinatal period. © 1979.