4(R)-5, 10, Seco 19-Norpregna 4,5 Diene 3, 10, 20 Trione (Seco), an Inhibitor of Epididymal 5α-Reductase Arrests Sperm Forward Motility in Wistar Rats

The effect of 4(R) - 5, 10, Seco 19 - norpregna 4,5 diene 3,10, 20 trione (SECO), a potent inhibitor of 5α-reductase, an intracellular enzyme that converts testosterone to dihydrotestosterone (DHT), on epididymal sperm count and motility was studied in Wistar rats. Administration of (i.m.) 250, 500, 750,1000 μg SECO/Kg b.wt/day to mature rats for 45 days impaired sperm forward motility in a dose dependent manner. Epididymal weight and sperm number decreased in rats treated with 750 and 1000 μg SECO, whereas weight of other accessory organs decreased in rats treated with 1000 μg SECO only. The epididymal histology showed degraded sperm and increased number of clear cells indicating high endocytotic activity, to clear dead sperm, whereas no obvious change was observed in the testicular histology. SECO treatment increased testosterone concentration whereas, it decreased estradiol concentration in circulation and in the epididymal tissue. SECO treatment specifically decreased 5α-reductase in epididymis without affecting the same in the liver, indicating its targeted effect on the epididymis. Thus, the preliminary in vivo study points out that SECO impairs the acquisition of sperm forward motility.