Possible mechanism for the first response to short captivity stress in the water frog, Rana esculenta

Abstract

Abstract To clarify the endocrine mechanism involved in the short captivity stress in the water frog, Rana esculenta, the activity of 9-ketoreductase, the enzyme which converts prostaglandin E2 (PGE2) into prostaglandin F2α (PGF2α), and aromatase, which converts testosterone into oestradiol-17β, were studied. Adult male and female frogs were sacrificed 0, 1·5, 3, 6, 12, 24, 48, 72, 168 and 336 h after capture in the field. PGE2, PGF2α, progesterone, testosterone, oestradiol-17β and corticosterone plasma levels were detected by RIA at each time point. 9-Ketoreductase (conversion of [3H]PGE2 into [3H]PGF2α) and aromatase (conversion of [3H]testosterone into [3H]oestradiol-17β) activities in the brain, testis, ovary and interrenal were also determined at each time point. After capture, levels of plasma PGF2α increased (male: 228%; female: 288%) and PGE2 decreased (male: 68%; female: 81%) at 1·5 h, oestradiol-17β increased (male: 399%; female: 425%) and testosterone decreased (male: 87%; female: 83%) at 6 h, and corticosterone increased (male: 421%; female: 426%) at 72 h. 9-Ketoreductase activity in the brain was enhanced at 1·5 h after capture (male: 249%; female: 262%); aromatase activity increased at 6 h in the testis (261%), ovary (273%) and interrenal (male: 227%; female: 267%). These results indicate that short captivity stress could induce an increase in plasma PGF2α through activation of brain 9-ketoreductase. In turn, PGF2α might enhance the levels of circulating oestradiol-17β through activation of gonadal and interrenal aromatase. Journal of Endocrinology (1996) 148, 233–239