Accumulation of copper on albumin in bovine plasma in vivo after intravenous trithiomolybdate administration.

The initial disappearance of intravenously administered copper (10 to 20 mg) from bovine plasma in vivo was delayed by the intravenous injection of trithiomolybdate (20 to 75 mg molybdenum per 400 to 445 kg steer); however, the most characteristic effect was the retention of up to about 0.5 mg copper per litre plasma for up to 24 hours after injection. Sephadex G-100 gel filtration of plasma samples showed that this retained copper was associated with the albumin fraction. The effect of trithiomolybdate was very dependent upon the interval between the injections of trithiomolybdate and copper. It is suggested that this variability was due to thiomolybdate metabolism. The infusion of trithiomolybdate (12 to 75 mg molybdenum) over 24 hours also caused the accumulation of albumin-bound copper. The amount bound did not exceed approximately 0.5 mg copper per litre plasma even when the diet of the steers was supplemented with copper sulphate or when copper sulphate (2 X 15 mg copper) was injected directly during the infusion. It is suggested that the longer term effects of trithiomolybdate are not merely a consequence of a simple copper-thiomolybdate reaction but result from three-way interactions between trithiomolybdate, albumin and copper, and that slow infusion of trithiomolybdate provides a model for the study of the systemic effects of dietary molybdenum in cattle.