The maximum capacity of the bovine liver to excrete manganese in bile, and the effects of a manganese load on the rate of excretion of copper, iron and zinc in bile.

1. The maximum capacity of the bovine liver to excrete manganese in bile was determined in three Friesian-cross steers surgically prepared to allow bile flow-rate to be measured and samples collected. Plasma Mn concentrations were increased by infusing manganese chloride solutions into a jugular vein and the biliary excretion rates of Mn, copper, zinc and iron were measured. 2. The maximum capacity of the liver to excrete Mn in bile was exceeded at an infusion rate of approximately 4000 microgram Mn/min, and at this rate there was a significant decrease in the concentration of Cu, Fe and Zn in bile. The maximum concentration (mean +/- SE) of Mn in bile was 193 +/- 19 microgram/ml, and the maximum excretion rate (mean +/- SE) was 1210 +/- 130 microgram/min for three animals. There was no reduction in bile flow or evidence of live damage as a result of the infusions.