Zinc deficiency affects the activity and protein concentration of angiotensin-converting enzyme in rat testes

Zinc (Zn) deficiency causes hypogonadism in a number of different species. Previous work has shown that Zn deficiency reduces the activity of angiotensin-converting enzyme (ACE), a Zn-dependent enzyme, in the testes of prepubertal rats. These studies were designed to determine whether this effect was caused by a change in the concentration of ACE protein. Thirty-five male rats at 26 days of age were divided into three groups. One group was fed ad libitum a Zn-adequate diet (40 mg/kg); another group was fed a similar diet, but deficient in Zn (< 1.0 mg/kg); a third group was pair-fed to the deficient group. After 4 weeks on these regimens, all rats in the ad libitum-fed group and half of the rats in each of the deficient and pair-fed groups were sacrificed, and tissues were collected for analysis. The remaining animals in the Zn-deficient and pair-fed groups were fed a Zn-adequate diet ad libitum for another 2 weeks, then sacrificed. With the use of an enzyme-linked immunosorbent assay for testicular ACE protein, the effect of these treatments on the concentration of ACE protein in testes was determined. After 4 weeks, ACE activity in testes of the Zn-deficient rats was reduced by 74% compared to that in the ad libitum-fed controls. This was accompanied by a 64% reduction in the amount of ACE protein in the testes. There was not a significant effect of pair-feeding. Refeeding Zn-deficient rats a Zn-adequate diet for 2 weeks restored ACE protein concentrations and ACE activity to values not significantly different from those in pair-fed controls. Soluble ACE, but not particulate ACE, of the epididymis was significantly reduced by Zn deficiency. Because the ACE activity of testes has been found primarily in the germinal cells, and soluble ACE in the epididymis is derived from the testes, these findings suggest that the effects of Zn deficiency on testicular and epididymal ACE is caused by an impairment of spermatid development.