Effects of high doses of molybdenum and sulphate on the distribution of copper in plasma and in blood of sheep

Abstract

Sheep on a daily intake of 120 mg molybdenum and 7.4 g sulphate for 29 months maintained plasma total copper concentrations at twice (P < 0.05) and plasma direct-reacting copper concentrations at 10 times (P < 0.01) the pre-experimental level. Plasma ceruloplasmin levels in these sheep were not significantly increased, but the copper concentration in the red cells was reduced to one-tenth of the normal level (1.0 µg/ml).

When the molybdenum dose was progressively diminished, plasma total copper and directreacting copper concentrations remained elevated above the normal until the molybdenum intake was reduced to 12 mg per day. The minimum concentration of copper in the red cells was induced when the molybdenum intake was 96 mg per day. Small amounts of copper detected in the ultrafiltrates of plasma from both treated and untreated sheep were independent of the total plasma concentration.

The correlation between non-direct-reacting copper and ceruloplasmin in the plasma, whether determined spectrophotometrically or by its oxidase activity, was high (r = 0.89, P < 0.01). This allowed the use of a regression equation to calculate the non-direct-reacting copper concentration of the plasma.

All the copper in the plasma from sheep on a high intake of molybdenum and sulphate could be accounted for in terms of direct-reacting copper, ceruloplasmin copper and ultrafiltrable copper. A significant decrease (P < 0.01) in the copper concentration of the wool was caused by treatment of the sheep with molybdenum and sulphate.

At the end of the period the haemoglobin concentration in the blood of the sheep on the continuous high dose of molybdenum and sulphate had fallen 30%, but the weight of the sheep was maintained, and apart from the condition of the wool, no clinical signs of copper deficiency were observed.