Effect of intratesticular administration of gonadotropins on testicular and plasma androgen concentration in the lizard, Uromastix hardwicki

An acute effect of intratesticular injections of varying doses of ovine FSH (NIH-FSH-S12), ovine LH (NIH-LH-S20), and a lizard hypophyseal extract was observed on testicular and plasma androgen concentrations in Uromastix hardwicki. FSH and LH were used in a dose range of 0.25–4.00 ng and the hypophyseal extract was administered at concentrations representing 10–160 μg of fresh pituitary tissue obtained from adult male Uromastix. The test material was injected directly into one testis while the contralateral testis was likewise treated with an equal volume of saline. The control lizards received intratesticular injections of saline on both sides. Testicular and plasma androgen concentrations were measured 3 hr following the injections, using a specific RIA for testosterone. A significant increase in androgen concentration both in the testis and the plasma was obtained with 0.25 ng of FSH and 4.00 ng of LH. Both FSH and LH induced a significant rise in plasma androgen at 1.00 ng, but the increase was markedly greater in the FSH treated lizards. The homologous hypophyseal extract was shown to be active at the minimum dose level used (10 μg). The testosterone content of the uninjected testis in treated lizards was not significantly different from that of the control lizards. It is concluded that the intratesticular route of administration can be used as a sensitive and rapid method for studying in vivo responsiveness of the testis to mammalian and nonmammalian gonadotropins.