Histological and endocrinological investigations of cyclosporine effects on the rat testis.

To investigate the effects of cyclosporine on spermatogenesis and endocrinological function of the testis, cyclosporine was administered subcutaneously to mature male Sprague-Dawley rats. Four and 6 weeks after the termination of cyclosporine administration (40 or 60 mg kg-1), the diameter of seminiferous tubules was diminished. The percentage of tubules with spermatozoa was decreased 6 weeks after the termination of cyclosporine treatment (20-60 mg kg-1). However, tubular wall thickness did not change throughout the experiment. Serum follicular stimulating hormone level increased significantly immediately after termination of cyclosporine administration dose-dependently, while the serum levels' luteinizing hormone and testosterone did not alter throughout the experiment. It is strongly suggested that cyclosporine impairs spermatogenesis and Sertoli cell function, although Leydig cell function is not injured.