The control of male fertility by 1,2,3-trihydroxypropane (THP;glycerol): rapid arrest of spermatogenesis without altering libido, accessory organs, gonadal steroidogenesis, and serum testosterone, LH and FSH.

This study examines the effects of intratesticular injection of aqueous 1,2,3-trihydroxypropane (THP; glycerol) solution on male reproductive biology. In a series of experiments, Sprague-Dawley rats of various ages (48-101 days) were injected with 50-200 microliters per testis and various parameters were studied for up to 21 weeks later. While an injection of THP resulted in testicular weight reduction of 45-60% within 2 weeks, the weights of prostate and seminal vesicles were not affected for the duration of the experiments. The number of sperm per epididymis in the THP-treated rats declined rapidly and was reduced by 99.99% (of controls) after the 3rd mating. THP-treated males mated with virgin females at the same frequency as control rats but all were infertile after the 3rd mating and remained infertile for the duration of the tests (21 weeks after treatment). In vitro studies showed that metabolism of 14C-progesterone by testicular homogenates was not altered quantitatively or qualitatively by THP treatment. Serum levels of androgens, LH and FSH of THP-treated rats did not differ significantly from the controls. Histologically and histochemically, the Leydig cells appeared to be normal, but the seminiferous tubules of THP-treated testes were devoid of spermatogenic cells within 2 weeks of a single treatment. It is concluded that direct injection of THP acts as a potent inhibitor of spermatogenesis resulting in long-term infertility without affecting steroidogenesis, libido, secondary sex characteristics, mating behaviour or serum hormone levels.