Effects of single and repeated administration of prostaglandin F2 alpha on secretion of testosterone by male rats.

The effects of single and repeated administration of prostaglandin (PG) F2 alpha on the secretion of testosterone and the effect of PGF2 alpha on the action of human chorionic gonadotropin (hCG) were investigated in adult male rats. The concentrations of plasma and testicular testosterone followed by a single injection of 100 micrograms of PGF2 alpha into each testis were similar to controls given a single injection of 0.05 ml of vehicle into one testis. When 1 or 10 IU of hCG were injected into the jugular vein simultaneously with the intratesticular injection of PGF2 alpha, concentrations of testosterone increased in response to dose; again, the effect was similar in controls. When 100 micrograms of PGF2 alpha was injected into each testis daily for 5 days, plasma testosterone concentration decreased below that in the controls, but the LH concentration was unchanged. When 1 or 10 IU of hCG were injected into the jugular vein the day after the fifth injection of PGF2 alpha, concentrations of plasma and testicular testosterone increased in response to dose; the effect was similar in controls. These results indicate that repeated stimulation by PGF2 alpha directly inhibits testosterone production in the rat testis without mediation by LH, and that PGF2 alpha does not affect the action of an LH-like substance.