Effects of mammalian gonadotropins (FSH and LH) on the testes of the lizard Anolis carolinensis

Abstract

Responses of the testis to mammalian FSH and LH were examined in the lizard Anolis carolinensis at different times of year and at different temperatures. Small amounts of FSH (0.1 mU/day) maintain testis weight and the accessory structures (epididymis and sex segment of kidney) and promote the development of new germ cells in surgically hypophysectomized lizards at 31° during the spring. Ovine LH has the same actions but much higher doses are required. With testosterone the rate of posthypophysectomy regression is reduced but no new germ cells develop. Both ovine FSH and LH stimulate spermatogenesis and interstitial cell activity in “physiologically” hypophysectomized Anolis at 31° in the fall. The development of accessory sexual structures requires a higher dose of gonadotropin than does complete spermatogenesis; only the early stages of spermatogenesis—up to the spermatid stage—occur with low doses of gonadotropin. Comparison of several preparations of ovine gonadotropins (from NIH and Papkoff) indicates that the potency of FSH is many hundred times greater than that of LH with regard to the stimulation of spermatogenesis and interstitial cell activity in the lizard. At 20°, the high doses of gonadotropin required to initiate the development of accessory sexual structures cause an abnormal—edematous—response in the germinal epithelium. Normal spermatogenic recrudescence at 20° is mimicked best by a relatively low dose of gonadotropin which does not promote interstitial cell activity. The observed thermal effects and differential dose sensitivity of various testicular responses suggest that annual cycles of spermatogenesis and interstitial cell activity in reptiles may result from variations in the level of a single gonadotropin (or gonadotropic-complex). A scheme is proposed whereby low temperatures suppress circulating gonadotropins so that only the early stages of spermatogenesis occur, while increased temperatures elevate gonadotropin production which leads to the development of accessory sexual structures and spermiation.