Effect of vitamin D repletion on testicular function in vitamin D-deficient rats

Freshly weaned 30-day-old male Wistar rats were fed a vitamin D-deficient diet adequate in calcium and phosphorus for 3 months. On the 120th day of age three different doses of vitamin D were injected intramuscularly into three groups of rats and maintained for another month with water and a normal diet ad libitum. One group was continued with a vitamin D-deficient diet up to the 150th day. One group of animals was killed by decapitation on the 120th day and testicular functions like sperm count in testis and epididymis, testicular glutamyl transpeptidase activity and Leydig cell count as well as body weight were noted. On the 150th day animals of all groups were killed and testicular function was studied. Body weight and testicular function decreased significantly on the 120th and 150th day of age in vitamin D-deficient rats as compared to age-matched normal control rats. Injection of lower doses of vitamin D on the 120th day of age improved testicular function after 1 month whereas administration of a high dose of vitamin D caused a deterioration of the testicular function. The result suggests that retardation of spermatogenesis due to disturbances in Sertoli and Leydig cell function in vitamin D deficiency is reversible and can be corrected by supplementing an optimal dose of vitamin D.