Studies on poisonous metals. XIII. Effect of cadmium on small intestinal absorption of L-histidine in rats.

Abstract

The effect of cadmium on the small intestinal absorption of L-histidine was studied. The absorption of L-histidine (0.19-3.23 mM) from the small intestine of rats in situ was significantly depressed in the presence of cadmium (10-13 μg/ml) in the lumen. The absorption of L-histidine from the small intestine, after pretreatment with cadmium solutions (10 and 30 μg/ml) for 60 min, was significantly depressed as compared with the control. In addition, the absorption of L-histidine from the intestine of rats in situ at 1 and 5 h after a single oral administration of cadmium (3 mg/kg) was significantly decreased as compared with the control, although there was no significant decrease of absorption of L-histidine at 8 and 12 h after the administration of cadmium. In view of the accumulation of cadmium in the intestinal tissue and the result of Sephadex G-75 filtration of intestinal soluble fraction, it seems likely that the depressed intestinal absorption of L-histidine was due to the effect of free cadmium in the intestinal tissue. An in vivo intestinal circulation experiment confirmed that cadmium taken up in the intestinal tissue inhibits the active transport of L-histidine across the rat small intestine.