T3 enhancement ofin vitro estradiol-17β secretion by oocytes of rainbow trout,Salmo gairdneri, is dependent on cAMP.
The cellular mechanism of action of 3,5,3'-triiodo-L-thyronine (T3) in enhancing SG-G100 gonadotropin-induced ovarian secretion of 17β-estradiol (E2) was studiedin vitro using oocyte follicular preparations of rainbow trout. The dependence of the T3 stimulatory action on the level of intracellular 3',5'-cyclic adenosine monophosphate (cAMP) was shown in experiments in which forskolin or dibutyryl cAMP enhanced E2 secretion. In the presence of partially purified salmon gonadotropin (SG-G100), T3 stimulation of E2 secretion was prevented by theophylline, suggesting that T3 may exert part of its stimulatory action by inhibiting phosphodiesterase.
Department of Zoology, University of Manitoba, R3T 2N2, Winnipeg, Manitoba, Canada.
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Eales