Interdependence of routes excreting manganese 1

217-224. 1966. -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 two successive “waves.” The first wave reflected the initial plasma clearance, signaling direct passage of some manganese in the direction of a steep concentration gradient between plasma and bile. This concentration gradient became even steeper during the second wave. This wave preceded the one reported by others for bile acids. It could be abolished by feeding low-manganese milk, but it was reinduced promptly by injecting manganous sulfate into the duodenal lumen. Increasing the manganese loads increased the duration rather than the height of this wave. Since both the artificial and the natural manganese 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.