Effects of Ethanol on the Transport of Manganese by Small Intestine of the Rat

Previously published studies have shown an increase of hepatic manganese in rats chronically fed ethanol. In this study both in vitro and in vivo experiments were conducted to demonstrate whether ethanol influences intestinal absorption of manganese and it also sought to separate the direct effects of ethanol from its metabolic effects on the transmural movement of manganese across the intestine. The transmural movement of manganese was measured in isolated loops of rat jejunum and compared to that obtained when the perfusate on the mucosal side of the tissue contained 3% ethanol. In in vivo studies, fasted rats were gavaged with 0.01 μCi 54Mn in the presence of either water or ethanol solution (4 g/kg body weight). After 3 hours the livers were excised and counted for radioactivity. In the in vivo experiments, ethanol stimulated the absorption of manganese twofold as measured by the uptake of this metal in the liver. The results of the in vitro experiments demonstrate that ethanol stimulated the transmural movement of manganese by a factor of four. Pyrazole, an alcohol dehydrogenase inhibitor, was found to reduce ethanol-induced transport of Mn by 70% in the perfused jejunum indicating that the effects of ethanol are principally mediated by metabolism of ethanol in the gut.