title: Mechanism of hCG-induced spermiation in the toad Rhinella arenarum (Amphibia, Anura).
abstract: In Rhinella arenarum spermiation occurs as a consequence of LH/FSH increase during the amplexus or by a single dose of hCG, among other gonadotropins. The present study employs an in vitro system to study the mechanism of action of hCG in the spermiation of R. arenarum. Testicular fragments were incubated for 2h at 28°C in the presence or absence of 20IU hCG with or without different PKA/PKC inhibitors and activators as well as ouabain and amiloride as Na(+)/K(+) ATPase and transcellular Na(+) transport inhibitors, respectively. Ouabain did not induce spermiation in absence of hCG and inhibited hCG-induced spermiation in a dose-dependent manner, reaching 90% inhibition with the higher concentration. In contrast, amiloride neither affected spermiation nor steroidogenesis. Activation of PKA with 8Br-cAMP induced spermiation in the absence of hCG while its inhibition with H89 blocked hCG action. On the other hand, PKC inhibition with Bi or STP did not affect hCG-induced spermiation although PKC activation significantly decreased hCG-dependent sperm release. These results suggest that PKC inhibits spermiation but also that the inhibition exerted by the kinase could be blocked by hCG. Taken together, these observations could indicate that PKA is involved in the mechanism of the gonadotropin action, mechanism also requiring the activation of a non-pumping Na(+)/K(+) ATPase pathway.
authors.affiliation: Laboratorio de Endocrinología Comparada, Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina. claravolonteri@bg.fcen.uba.ar
authors.forename: M Clara
authors.initials: MC
authors.lastname: Volonteri
authors.forename: Nora R
authors.initials: NR
authors.lastname: Ceballos
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000584:Amiloride / Q000493:pharmacokinetics; D000818:Animals; D002022:Bufo arenarum / Q000502:physiology*; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D007211:Indoles / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology*; D011493:Protein Kinase C / Q000378:metabolism; D012708:Sertoli Cells / Q000187:drug effects; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D013094:Spermatozoa / Q000187:drug effects / Q000378:metabolism*; D019311:Staurosporine / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D006063:Chorionic Gonadotropin; D007211:Indoles; D007546:Isoquinolines; D008301:Maleimides; D013449:Sulfonamides; D015124:8-Bromo Cyclic Adenosine Monophosphate; D010042:Ouabain; D000584:Amiloride; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D000254:Sodium-Potassium-Exchanging ATPase; D019311:Staurosporine; C070515:bisindolylmaleimide I; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D013755:Tetradecanoylphorbol Acetate