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.

Calbindin-D9k expression in the pregnant cow uterus and placenta.

Calbindin-D9k (CaBP9k) is a vitamin D-dependent, calcium binding protein first identified in the cytoplasm of the intestinal epithelial cell. Using biotin-streptavidin immunohistochemistry, CaBP9k was localized to the maternal caruncular epithelium, fetal chorionic epithelium, and trophoblastic binucleated cells of the bovine placenta. Within the maternal epithelium the intensity of staining increases from second trimester pregnancies to term pregnancies, indicating a higher intracellular concentration of CaBP9k in the epithelium at term. Luminal and glandular epithelium of the non-caruncular endometrium also stained positively for CaBP9k in all stages of pregnancy observed. No CaBP9k was identified within the stroma or myometrium of the pregnant cow uterus. The increased level of CaBP9k in the caruncular epithelium during the last trimester is hypothesized to be in response to the rising demand for calcium to aid in the mineralization of the fetal skeleton. CaBP9k may play a role in enhancing calcium transport across the placenta in cattle.