Some studies on the metabolism of labelled molybdenum compounds in cattle

An initial experiment showed that 99Mo]di- and trithiomolybdates could be detected in bovine plasma after the introduction of 99Mo]molybdate into the rumen. It was felt that this justified the use of 99Mo]trithiomolybdate for the subsequent studies made of plasma thiomolybdate metabolism in vivo in cattle. Rapid intravenous injection of 99Mo]trithiomolybdate into cattle showed that doses of 50 mg Mo were subject to extensive hydrolysis over the first few minutes postinjection, but at lower dose rates this was reduced so that tracer doses (less than 1.5 mg Mo) were relatively stable. The plasma metabolism was unaffected by copper status within the limits of the experiments (that is, liver copper levels down to 9 mg/kg d.m.) The disappearance of 99Mo] and 35S]trithiomolybdate (1 mg Mo) from plasma was delayed for up to 10 hr by the immediate preinjection of copper, although no chemical modification of the thiomolybdate appeared to occur.