INFLUENCE OF ASCORBIC-ACID SUPPLEMENTATION ON COPPER-METABOLISM IN RATS

An attempt was made to unravel further the mechanism by which high dietary concentrations of ascorbic acid influence copper metabolism. The addition of ascorbic acid to the diet of rats caused about a twofold increase in plasma ascorbate concentrations and reduced group mean plasma and tissue concentrations of Cu. The effect of 10 g ascorbic acid/kg diet was greater than that of 1 g/kg. Ascorbic acid feeding reduced blood haemoglobin concentrations and packed cell volume values. Dietary ascorbic acid caused a significant decrease in apparent Cu absorption from the intestine. Ascorbate, intravenously administered together with Cu-64, caused an increase in Cu-64 in the liver. Ascorbate, at concentrations occurring in plasma after ascorbic acid feeding, promoted the uptake of Cu-64 by isolated hepatocytes. Thus, ascorbate stimulated the efficiency of hepatic uptake of Cu. Ascorbate, intravenously administered together with Cu-64, stimulated accumulation of Cu-64 in bile of rats with a bile duct cannula. In rats fed on ascorbic acid, intravenously administered Cu-64 was recovered in bile at increased rates. Dietary ascorbic acid enhanced the recovery of intraperitoneally administered Cu-64 in faeces. The ascorbate-induced stimulation of biliary Cu-64 excretion may reflect an increased hepatic uptake of Cu-64 and be caused by an increased specific activity of Cu in fiver pools. It is suggested that dietary ascorbic acid reduces tissue Cu concentrations primarily by interfering with intestinal Cu absorption. Ascorbate increases the efficiency of hepatic uptake of Cu, but this effect may not be causatively related with the reduced tissue Cu concentrations after ascorbic acid feeding.