Light and electron microscopic study of the toxic effect of prolonged lead exposure on the seminiferous tubules of albino rats and the possible protective effect of ascorbic acid
Lead has been long recognized as an occupational toxicant. Now, lead is considered to be one of the major environmental pollutants which have serious potential threat to human health. Reports of declining male fertility have renewed interest in the role of environmental and occupational exposures in the etiology of human infertility.The aim of the present work was to investigate the toxic effect of prolonged exposure to lead on albino rat's seminiferous tubules and the possible protective effect of ascorbic acid (vitamin C) on lead toxicity.The study was carried out on 40 adult male albino rats divided into three groups: a control group which comprised three subgroups; negative control which received no treatment and two positive controls receiving an oral daily dose of distilled water or ascorbic acid, respectively. Lead acetate--intoxicated group received lead acetate orally in a dose of 25 mg/kg b.w dissolved in distilled water for 3 months. While the protected group received ascorbic acid orally in a dose of 100 mg/kg b.w daily for 3 months, simultaneously with lead acetate in a similar dose to that of the intoxicated group. By the end of the experimental period, blood samples were collected for estimation of blood lead level. Fresh specimens were taken from the testis and processed for light and electron microscopic examination.Biochemical analysis demonstrated significant increase in the blood lead level in lead intoxicated group compared to the control group, while ascorbic acid--protected group revealed significant decrease in the blood lead level. Light microscopic examination of lead treated group revealed loss of normal architecture of the testicular tissue in the form of thin walled seminiferous tubules with wide lumen and vacuolations in the spermatogenic epithelium mostly separating primary spermatocytes from spermatogonia and surrounding nuclei of Sertoli cells. Apoptotic bodies were found among the basal part of the spermatogenic epithelium. Ultrastructural examination of the same group revealed degenerating cells with cytoplasmic vacuolations, apoptotic cells with heterochromatic nuclei and dense cytoplasm, irregularities in the basal lamina with increased collagen deposition and shrunken myoid cells. Late differentiating spermatids showed deformed head with widening of the subacrosomal space and redundant acrosome, in addition to the abnormalities in the tail of developing sperms. On the other hand, ascorbic acid--protected group showed amelioration of most of the degenerative changes depicted in the lead intoxicated group.Lead had an injurious effect on the testis of the exposed animals. Simultaneous administration of ascorbic acid was efficient in preventing most of such toxic effect and decreasing the blood lead level. Therefore, ascorbic acid can be recommended for protection against lead intoxication.