[Accumulation of cyclic adenosine monophosphate in the ovary of the eel (Anguilla anguilla L.) in vitro under the effect of carp gonadotropin or ovine lutropin: kinetics and thermodependence].
Cyclic AMP (cAMP) in pieces of eel ovary was greatly increased in vitro by the gonadotropin (cGTH) of carp, another teleost fish; after one hour at 20 degrees C, maximal stimulation = 31.7 and E.D. 50 = 0.08 micrograms/ml. Ovine lutropin (oLH) had less effect (maximal stimulation: 2.35; E.D. 50: 1.42 micrograms/ml); its action suggested that it involved a subfraction (oLH/cGTH RAc) of the receptor-adenylate cyclase (RAc) systems which mediate the action of cGTH. Another difference was the percentage of total cAMP accumulated under hormonal stimulation and released into the incubation medium; this percentage was much higher with oLH than with cGTH (47 vs 8% after one hour at 20 degrees C). This result might be explained by a localization of oLH/cGTH RAc in cells (theca ?) situated on the outside of the follicles and/or by a relative lack of cAMP binding proteins in the case of cAMP produced by oLH/cGTH RAc. Kinetic and thermodependence studies also disclosed hormone-dependent differences; at 5 degrees C, cAMP concentration was maximal after 40 min with oLH, whereas it was still increasing after 3 h with cGTH. Differences in the properties of phosphodiesterases and/or in the clearance rate of hormone-receptor (HR) complexes could explain these results. The set of RAc systems in eel ovary recognizing fish gonadotropin would then be heterogeneous; some of them would be endowed with original properties concerning receptor specificity and cAMP diffusion as well as associated phosphodiesterase activity and/or HR metabolism. We suggest that at a stage of evolution when a single sensu stricto GTH is present (instead of two in tetrapods), "isoreceptors", differing in specificity and in their fate after hormone binding, could be an important element in the fine regulation of gonadal functions.
D000818:Animals; D002347:Carps / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D003530:Cyprinidae / Q000378:metabolism*; D004524:Eels / Q000378:metabolism*; D005260:Female; D006062:Gonadotropins / Q000494:pharmacology*; D006358:Hot Temperature; D066298:In Vitro Techniques; D007986:Luteinizing Hormone / Q000494:pharmacology*; D010053:Ovary / Q000187:drug effects / Q000378:metabolism*; D012756:Sheep; D013997:Time Factors
D006062:Gonadotropins; C044396:carp gonadotropin; D007986:Luteinizing Hormone; D000242:Cyclic AMP
Accumulation du monophosphate cyclique d'adénosine dans l'ovaire d'anguille (Anguilla anguilla L.) in vitro sous l'effet de la gonadotropine de carpe ou de la lutropine ovine: cinétique et thermodépendance.