Effects of age and calcium ion on testis carbonyl reductase in rats

To examine the role of carbonyl reductase (CR) in the development and function of testis, age-related changes in CR and the effect of exogenous calcium on CR in rat testis were studied. Testicular CR activity was the highest at 3 weeks of age when the enzyme activity was measured at 2, 3, 4, 8 and 20 weeks of age. The intensity of positive protein bands in testicular cytosol was similar among these age groups in Western blot analysis with anti-rat ovarian CR antibody. In 3-week-old rats, intravenous administration of 4 mg/kg calcium markedly suppressed the activity to about 50% of the control level 1 min after the treatment. Pretreatment with nicardipine prevented the inhibitory effect of exogenous calcium on the testicular CR activity in 3-week-old rats, indicating that the suppressing action of calcium on the enzyme activity was mediated by the entry of extracellular calcium via calcium channels. There were no significant changes in the CR activity following the treatment with calcium and nicardipine in the other 3 age groups examined. These findings suggest that testicular CR plays an important role in the functional development of the testis during the infantile period in rats.