Effect of vitamin D on testicular CaBP28K expression and serum testosterone in chickens

Vitamin D is known to reverse infertility in male and female rats. This study was an investigation of the effects of vitamin D deficiency on calbindin-D28K (CaBP28K) and testosterone levels in male chickens. Chickens were raised from 1 day of age to 8 wk of age on a normal or a vitamin D-deficient diet. A radioreceptor assay showed that serum vitamin D levels were significantly higher in chickens fed a normal diet than in those fed a vitamin D-deficient diet. The morphology of the seminiferous tubules was not different between the vitamin D-replete and vitamin D-deficient chickens. Immunohistochemical studies revealed that CaBP28K was present in spermatogonia and spermatocytes of the seminiferous tubules. A few interstitial Leydig cells were positive for CaBP28K. RIA was used to quantify the amount of CaBP28K in the testes, which was threefold higher in chickens raised on a normal diet than in chickens raised on a vitamin D-deficient diet. Testosterone concentration in serum, determined by RIA, was not different between the two groups. Neither serum calcium nor phosphorus levels were different between the two groups. This investigation represents the first demonstration of the effect of vitamin D deficiency on CaBP28K expression in chicken testes. The results indicate that the decrease in testicular CaBP28K concentration was attributable to vitamin D deficiency despite normal serum testosterone and calcium levels in 8-wk-old chickens.