Aconitase activity, citrate oxidation, and zinc inhibition in rat ventral prostate

Aconitase activity and citrate oxidation were determined in mitochondrial preparations from rat ventral prostate. Aconitase activity in prostate mitochondria was approximately 10% of the activity observed in kidney preparations. The prostate aconitase activity was completely inhibited by the addition of 1.0 mmol/l zinc and kidney aconitase was inhibited by approximately 50%. The presence of 1.0 mmol/l zinc also markedly inhibited the formation of isocitrate from cis-aconitate. The reduction of NADP by citrate was markedly inhibited (approx. 95%) by 1.0 mmol/l zinc as compared with a 70 and 40% inhibition of aconitate--and isocitrate--stimulated reduction, respectively. These results indicate that zinc might be a strong inhibitor of aconitase activity with an inhibitory effect on isocitrate dehydrogenase also. The effect of 1.0 mmol/l zinc on citrate oxidation was studied by determining 14CO2 production from 6-14C-citrate. 14CO2 was significantly inhibited by zinc. These results further corroborate the conclusion that citrate accumulation in prostate might be the result of limited citrate oxidation which results from a combination of low aconitase activity and possibly zinc inhibition.