Previous studies showed considerable decrease of epididymal sperm count in diabetic rats and ascribed it to spermatogenic damage in the testis; diabetic rat models were therefore often used for pharmaceutical studies on sperm protection. But there were methodological problems with previous studies: sperm count obtained in many studies does not represent the total sperm storage and spermatogenic damage was not reliably evaluated with quantitative (stereological) methods. The present study aimed to determine with stereological methods whether the rat diabetes reduces sperm storage and damages spermatogenesis. 44 normal rats and 9 unilaterally vasectomized rats were induced diabetic with streptozotocin treatment; epididymides and testes were obtained at 14 days, 30 days, and 12 weeks after the treatment. Stereological measurements were implemented on methacrylate embedded epididymal and testicular sections. Total volumes of sperm mass and other tissues in the epididymis were estimated; testicular histology, seminiferous tubule diameters, and others were evaluated. The results demonstrated that total volumes of sperm mass and its surrounding epididymal tissues in the epididymides decreased significantly by more than 40%−61% and 18%−26%, respectively, 2−12 weeks after induction of diabetes in mature rats while spermatogenic damage was not prevalent, with most of the diabetic rat testes having normal spermatogenesis. The total volume of sperm mass in the epididymis plus sperm granuloma (formed around the vas deferens after vasectomy) on the vasectomized side was not significantly decreased in normal (without spermatogenic damage) diabetic rats compared with normal non‐diabetic rats (unilaterally vasectomized). In conclusion, type I diabetes in rats indeed results in considerable reduction of the epididymal sperm reserve. But probably it is mainly the result of atrophy of the epididymis and hypercontractility of the epididymal duct due to decreased serum testosterone levels commonly seen in diabetic rats, not the result of reduced sperm production.
Ma et al. (Thu,) studied this question.