EFFECTS OF GONADECTOMY AND TEMPERATURE ON THE N-ACETYLTRANSFERASE ACTIVITY IN THE HARDERIAN-GLAND OF THE GREEN FROG RANA-ESCULENTA

Since, in the Harderian gland (HG) of the hamster, the N-acetyltransfe rase (NAT), the specific enzyme involved in the biosynthesis of melato nin, exhibits a sexual dimorphism, in the present study, we investigat ed whether such a dimorphism is present also in the HG of the green fr og Rana esculenta. In intact frogs, no significant differences emerged between males and females in the HG NAT activity under both cold (10 degrees C) and warm (22 degrees C) temperature conditions, In female f rogs, the HG NAT activity was significantly decreased by both gonadect omy (P < 0.001) and warm temperature (P < 0.001), the two effects bein g not additive. In male animals, neither gonadectomy nor temperature a lone significantly affected the activity of the NAT enzyme in the HG. However, gonadectomized male frogs exposed to warm temperature exhibit ed a significant drop in the HG NAT activity (P < 0.005), These data s how that, in Rana esculenta, although no sexual dimorphism exists in t he HG NAT activity, a sex difference is evident in the modulation of t he enzyme activity by gonads and temperature, the female frogs being m ore sensitive to the impairing effects of both gonadectomy and higher temperature.