[en] Previously we have demonstrated an increase during midlactation in ¹⁰⁹Cd adsorption and increased retention by the duodenum, kidney, and mammary tissue of mouse dams receiving environmental levels of cadmium/¹⁰⁹Cd via drinking water, with little change in ¹⁰⁹Cd retention in liver and jejunum compared to nonpregnant controls. Results are reported here of a study of cadmium deposition during midlactation as associated with induction of metallothionein (MT). A cadmium/hemoglobin (Cd/Hb) assay and radioimmunoassay for MT which measures heat-stable cadmium binding capacity in tissues was used to determine MT concentrations in fractions of kidney, liver, duodenum, and jejunum from female mice. Both assays demonstrated clear lactation-induced increases in MT concentrations in liver, kidney, and duodenum, with MT concentrations falling rapidly to control levels after weaning. 4 refs., 1 tab

[en] Results are reported of a study conducted to test the hypothesis that increases in cadmium deposition during midlactation are caused by an induction of the metal-binding protein, metallothionein (MT). A cadmium/hemoglobin (Cd/Hb) assay for MT (which measures heat-stable cadmium binding capacity in tissues) was used to determine MT concentrations in the heat-treated supernatant fractions of kidney, liver, duodenum, and jejunum from five groups of B6CF1/ANL female mice. Portions of the same supernatants were also analyzed for MT by radioimmunoassay (RIA). Results show that metallothionein (or an MT-like cadmium-binding protein) increases in concentration in liver, kidney, and duodenum of mouse dams during lactation and decreases to levels found in nonpregnant controls by 5 days after weaning. They have evidence that the MT that appears in the liver of midlactating mice exists in two forms, a native form that chromatographs with a Ve/Vo = 1.6 and reacts strongly with MT antibody, and a second form that appears with heating or storage in the freezer (data not shown), reacts less strongly with MT antibody, and chromatographs with a lower apparent molecular weight (Ve/Vo = 2.2)