Maximum capacity of the bovine liver to remove manganese from portal plasma and the effect of the route of entry of manganese on its rate of removal.

The rate of uptake of manganese by the liver was measured during infusions of manganese into either the visceral or the systemic circulation of four cows surgically prepared with cannulae in a mesenteric vein, the portal vein and a hepatic vein and in one carotid artery. In three experiments the maximum capacity of the liver to remove manganese from plasma was measured by infusing manganese chloride solution into a mesenteric vein at increasing rates for six hours. In two experiments the rate of uptake of manganese by the liver was determined during infusions of manganese chloride solution into a jugular vein for six hours at a constant rate. Virtually all the manganese infused into a mesenteric vein was cleared during its first pass through the liver, up to a maximum rate (mean +/- SEM) of 97.1 +/- 14.1 mumol per minute or 12.7 +/- 2.3 mumol per minute per kg of liver weight. However, when manganese was infused into a jugular vein at rates less than this maximum rate of uptake only approximately 50 per cent of the manganese in portal plasma was removed during a single passage through the liver.