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-acetyltransferase (NAT), the specific enzyme involved in the biosynthesis of melatonin, exhibits a sexual dimorphism, in the present study, we investigated whether such a dimorphism is present also in the HG of the green frog 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 frogs, the HG NAT activity was significantly decreased by both gonadectomy (P < 0.001) and warm temperature (P < 0.001), the two effects being not additive. In male animals, neither gonadectomy nor temperature alone significantly affected the activity of the NAT enzyme in the HG. However, gonadectomized male frogs exposed to warm temperature exhibited a significant drop in the HG NAT activity (P < 0.005). These data show that, in Rana esculenta, although no sexual dimorphism exists in the HG NAT activity, a sex difference is evident in the modulation of the enzyme activity by gonads and temperature, the female frogs being more sensitive to the impairing effects of both gonadectomy and higher temperature.
Dipartimento di Fisiologia Umana e Funzioni Biologiche Integrate Filippo Bottazzi, Seconda Università degli Studi di Napoli, Italy.
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I
Serino
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P
Monteleone
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M
d'Istria
D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000378:metabolism*; D005260:Female; D006243:Harderian Gland / Q000201:enzymology*; D008297:Male; D009919:Orchiectomy; D010052:Ovariectomy; D011893:Rana esculenta / Q000502:physiology*; D012727:Sex Characteristics; D013696:Temperature
D001191:Arylamine N-Acetyltransferase