Reduction of fertility in the male rat by systemic treatment with follicle regulatory protein

Forty-five-day-old rats daily injections of follicle regulatory protein (FRP). After 15, 30, 45, and 70days of therapy, serum was measured for testosterone, androstenedione, estradiol, and follicle-stimulating hormone levels. Testes were evaluated for sperm head counts, plasminogen activator activity, weight, and length of seminiferous epithelial stages. In no case was serum follicle-stimulating hormone concentration reduced in FRP-treated rats. After 75days of treatment, there was a significant decrease in the number of the sperm head counts. After 60days of treatment, the length of the dark zone of the tubule was longer than that of control. Pregnancy rates for FRP-treated rats were reduced after 45 and 60days of treatment. In conclusion, systemic injection of FRP alters seminiferous epithelial function by reducing development of mature sperm.