EFFECTS OF MELATONIN ON GONADAL-STEROIDS AND GLUCOSE PLASMA-LEVELS IN FROGS (RANA-PEREZI AND RANA-TEMPORARIA)

The effect of melatonin treatment on the Gonosomatic Index (GSI), ovarian germinal epithelium, plasma estradiol and testosterone levels was studied in Rana perezi females in December. No significant changes were observed in GSI, estradiol, and testosterone levels in melatonin treated animals when compared with saline injected controls, but the percentage of previtellogenic follicles decreased in animals treated with melatonin (100 μg). The effect of melatonin treatment on glucose level was studied in Rana perezi females in December and Rana temporaria males in February. In Rana perezi no significant differences were observed between melatonin treated and control animals; however, significant reductions by melatonin treatment were obtained in Rana temporaria. The possibility that the inhibitory effect of melatonin can be observed only when gonadal function and metabolism are stimulated by temperature is discussed. Copyright © 1990, Wiley Blackwell. All rights reserved