In vitro inhibition of estradiol secretion of tadpole ovaries by cyanoketone.
We have demonstrated the presence of delta 5-3 beta-hydroxysteroid dehydrogenase (HSD) activity in tadpole ovaries of Rana catesbeiana. In the present study, we wish to determine whether estradiol (E2) secretion of tadpole ovaries could be influenced by cyanoketone (CK), a specific inhibitor of delta 5-3 beta-HSD. R catesbeina tadpoles at the premetamorphic climax were used, and pooled ovaries were incubated, 30 mg/tube, with CK at dosages of 0, 0.001, 0.01, 0.1, 1, and 10 micrograms/ml of Krebs-Ringer bicarbonate buffer for 6 hr. Media were collected for assay of E2 by radioimmunoassay (RIA). Results showed an inhibition of E2 secretion by CK that was positively correlated with CK dosage, but plateaued at doses of 0.1 microgram/ml and higher. This finding was comparable to that of G.F. Young, H. Kagawa, and Y. Nagahama (1982, Gen. Comp. Endocrinol. 47, 357-360) on adult fish ovaries. However, adult vertebrates depend on gonadotropins to regulate secretion of E2 while tadpoles, being immature, might secrete E2 independently of pituitaries. When the histochemical test for delta 5-3 beta-HSD activity was performed on in vitro CK-treated ovaries, there was a decrease of enzyme activity by CK. The RIA and histochemical findings may contribute to the concept of sex transformation in which a disturbance of steroidogenesis may induce sex reversal from females to males, at least in tadpoles.
Hsu
C Y
CY
Department of Biomorphics, National Defense Medical Center, Taipei, Taiwan, Republic of China.
Chang
L T
LT
Yu
N W
NW
Ku
H H
HH
Lu
M H
MH
D000737:Androstenols / Q000494:pharmacology*; D000818:Animals; D003489:Cyanoketone / Q000494:pharmacology*; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D006651:Histocytochemistry; D066298:In Vitro Techniques; D007814:Larva / Q000187:drug effects / Q000378:metabolism; D010053:Ovary / Q000187:drug effects / Q000378:metabolism*; D011863:Radioimmunoassay; D011892:Rana catesbeiana / Q000378:metabolism*
D000737:Androstenols; D003489:Cyanoketone; D004958:Estradiol