The role of calcium ions in rat Leydig cell steroidogenesis induced by atrial natriuretic peptide.
The aim of this study was to clarify whether calcium ions play a role in the mechanisms by which rat atriopeptin II exerts its stimulatory effects on rat Leydig cell steroidogenesis. The absence of calcium in the medium and the calcium channel-blocker drug, verapamil, both significantly inhibited testosterone production in rat atriopeptin II-treated rat Leydig cells. Similar effects were observed on human chorionic gonadotropin-stimulated Leydig cells. Furthermore, 8-Bromoguanosine 3':5' cyclic monophosphate, the putative second messenger of atrial natriuretic peptide, significantly increased rat Leydig cell steroidogenesis, determining a stimulatory effect comparable to that obtained with rat atriopeptin II. Calcium-free medium and verapamil inhibited this stimulatory effect. The addition of a calcium ionophore. A-23187, significantly counteracted the inhibitory effect of verapamil on rat atriopeptin II-induced and 8-Bromoguanosine 3':5' monophosphate-induced testosterone production. Furthermore, rat atriopeptin II significantly stimulated the calcium flux through the plasma membrane, as evaluated by the 45Ca2+ uptake method. This effect was strongly inhibited by the addition of verapamil. These data underline that calcium ions may play a role in the mechanisms by which atriopeptin II stimulates rat Leydig steroidogenesis, although other post-receptor systems cannot be excluded.
III Chair of Medical Pathology, University of Padua, Italy.
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D000704:Analysis of Variance; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D002118:Calcium / Q000493:pharmacokinetics / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology; D002478:Cells, Cultured; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D000242:Cyclic AMP / Q000032:analysis; D006152:Cyclic GMP / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D007985:Leydig Cells / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010446:Peptide Fragments; D051381:Rats; D017207:Rats, Sprague-Dawley; D013739:Testosterone / Q000096:biosynthesis*; D013997:Time Factors; D014700:Verapamil / Q000494:pharmacology
D015220:Calcium Channels; D006063:Chorionic Gonadotropin; D010446:Peptide Fragments; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D009320:Atrial Natriuretic Factor; C062524:atrial natriuretic factor prohormone (103-125); D014700:Verapamil; D000242:Cyclic AMP; D006152:Cyclic GMP; D002118:Calcium