Interdependence of routes excreting manganese

Abstract

Radiomanganese (Mn54) was excreted by all intestinal segments investigated at several exponential rates. Yet the cephalad segments showed much higher excretion, which could be accelerated briskly by giving manganous sulfate, whereas excretion via the ileum could not. Intestinal excretion contrasted to biliary excretion: the tracer entered the bile in 2 successive "waves. " The 1 wave reflected the initial plasma clearance, signaling direct passage of some Mn in the direction of a steep concentration gradient between plasma and bile. This concentration gradient became even steeper during the 2 wave. This wave preceded the one reported by others for bile acids. It could be abolished by feeding low-Mn milk, but it was reinduced promptly by injecting MnSO4 into the duodenal lumen. Increasing the Mn loads increased the duration rather than the height of this wave. Since both the artificial and the natural Mn isotopes reflected these phenomena, it appeared that small amounts of the essential trace metal had saturated its enterohepatic circulation. The excess was apparently excreted via the duodenum and the jejunum.