Effects of exogenous prolactin on reproduction and growth in adult males of the lizard Anolis carolinensis

Abstract

Adult male Anolis were treated with 5–150 μg/day of exogenous ovine prolactin during the winter and spring under several different conditions of light and temperature. Calorimetric assays of various food insects were used to determine caloric assimilation rates. Prolactin increased food consumption markedly in the winter, when appetites were normally low, and promoted an increase in lean body weight, while fat depots in liver and abdominal fat pads were reduced. Thyroid epithelia were hypertrophied but metabolism was reduced with prolactin. Growth hormone in a dose (1 μg/day) equivalent to the maximum contamination expected in the prolactin preparation had no effect on the growth of Anolis. The natural increases in appetite during the spring obviated the action of prolactin on food consumption, but the hormone continued to exert a somatotropic effect. Prolactin-treated animals stored significantly less fat than controls. Increased body length occurred in prolactin-treated animals maintained on fluctuating temperatures (32-20°C) while the controls only fattened. Prolactin-treated lizards exposed to 32°C continuously did not grow in length but molted more frequently. Thyroid histology and metabolism were unaffected by prolactin during the spring. There was no effect of prolactin on the testes, during recrudescence in the winter or when fully active in the spring. Sexual behavior and accessory sex organs were also unaffected by prolactin, whereas 1 μg growth hormone stimulated accessory sexual structures.