Some studies on the metabolism and the effects of 99Mo- and 35S-labelled thiomolybdates after intravenous infusion in sheep.

Sheep were infused intravenously with 99Mo- and 35S-labelled tri- and tetrathiomolybdates (1-2 mg Mo). Most of the plasma radioactivity was trichloroacetic acid (TCA)-insoluble after infusion, but the stability of this fraction was reduced by pre-infusion or subsequent infusion with unlabelled thiomolybdates. Most of the 99Mo and 35S was shown to be associated with albumin. It was concluded that compounds bound to albumin were relatively stable, but displaced or unbound thiomolybdates were rapidly hydrolysed to molybdate and sulphate. There was no evidence of an irreversible interaction of either 35S or 99Mo with copper in plasma, despite the appearance of a TCA-insoluble Cu fraction. Increased dietary Cu did not increase the retention of 35S in plasma or affect the exchangeability of 36S-labelled thiomolybdates bound to albumin.