Effects of 17β-estradiol on liver vitellogenin geneexpression in immature female frogs, Hoplobatrachusrugulosus

摘要

We aimed to determine the vitellogenin gene expression in response to 17β-estradiol (E_2) treatment inlivers of immature female Chinese edible frogs (Hoplobatrachus rugulosus). Frogs reared during rainy or dry seasonswere intramuscularly injected daily with E_2at doses of 0, 50, 500, or 5000 μg/kg body weight for five days. During therainy season, treatment with E_2within the dose range studied significantly decreased the vitellogenin gene transcript levelscompared to those of the control. In contrast, during the dry season, treatment with E_2at all doses tended to increase thevitellogenin gene transcript levels. The endogenous plasma E2 levels in frogs reared during the rainy season were higherthan those reared during the dry season. There was no significant difference in liver-somatic index or gonadosomatic indexamong the treated frogs during the rainy season. However, during the dry season, the 500 μg/kg E_2treatment significantlyincreased the frog liver-somatic index. The hepatocytes from the dry season frogs appeared smaller and flatter. The histologyof ovaries from rainy season frogs showed that the oocytes were bigger and of several stages. We therefore concluded thatthe injection of E_2into immature femaleH.rugulosusmay stimulate vitellogenesis if administered during the dry season,when the endogenous E_2is lower. This knowledge could be used as a basis for inducing precocious maturation or mating ofH rugulosus outside the breeding season.