Effects of vitamin E deficiency and non-biological antioxidant (DPPD) on the function of the pituitary-gonadal axis of the rat

The effects of vitamin E deficiency on pituitary-gonadal function in rats and the preventive effects of N,N'-diphenyl-p-phenylene diamine (DPPD) administration were examined by measuring levels of pituitary and plasma follicle-stimulating hormone (FSH) and luteinizing hormone (LH), serum and testicular levels of testosterone, and affinity and receptor sites of FSH and LH in the testis by radioimmunoassay, at 180 days after feeding of a vitamin E-deficient diet and DPPD-administered diet. Light and electron microscopic examinations were also performed on the pituitary gland and testis. In the vitamin E-deficient rats, serum and liver alpha-tocopherol concentrations decreased significantly and erythrocyte hemolytic rate and serum and tissue malondialdehyde levels increased significantly. However, the increase of hemolytic rate and malondialdehyde concentration in the vitamin E-deficient rats was somewhat lessened by the administration of DPPD. In the vitamin E-deficient rats, the gonadotropic cells in the pituitary gland manifested accelerated secretory function indicated by enlargement of cells, development of Golgi apparatus and accumulation of secretory granules, while FSH and LH concentrations in the pituitary and serum were not affected by vitamin E deficiency. However, the testosterone concentrations in the plasma and testis were significantly lower in the vitamin E-deficient rats. The decrease of testosterone in plasma and tissue was prevented by the administration of DPPD, while the degeneration of seminiferous tubules was not completely restored by DPPD. It is concluded that DPPD can compensate to some degree for the lack of antioxidative activity due to vitamin E deficiency.