Involvement of T-type calcium channels in the mechanism of action of 5-HT in rat glomerulosa cells: a novel signaling pathway for the 5-HT7 receptor.
We have previously demonstrated that, in rat, the stimulatory effect of 5-HT on aldosterone secretion is mediated through a 5-HT7 receptor subtype. The aim of the present study was to characterize the transduction mechanisms associated with activation of native 5-HT7 receptors. 5-HT induced a dose-dependent increase in cAMP production in rat glomerulosa cells. Pretreatment of cells with the adenylyl cyclase (AC) inhibitor SQ 22536 or the protein kinase A (PKA) inhibitor H-89 markedly attenuated the effect of 5-HT on aldosterone secretion. Administration of 5-HT in the vicinity of glomerulosa cells induced a robust increase in cytosolic calcium concentration ([Ca2+]i) and this effect was abrogated by the T-type calcium channel blocker mibefradil. Patch-clamp studies confirmed that 5-HT activated a T-type calcium current. H-89 attenuated both the [Ca2+]i response and the activation of T-type calcium current induced by 5-HT. Reduction of extracellular calcium concentration in the medium or administration of mibefradil caused a marked reduction of the maximum effect (Emax) of 5-HT on aldosterone secretion. These data demonstrate that activation of native 5-HT7 receptors stimulates cAMP formation, which in turn provokes calcium influx through T-type calcium channels. Both the activation of the AC/PKA pathway and the calcium influx are involved in 5-HT-induced aldosterone secretion.
Lenglet
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European Institute for Peptide Research (IFRMP 23), Laboratory of Cellular and Molecular Neuroendocrinology, INSERM U413, UA CNRS, University of Rouen, 76821 Mont-Saint-Aignan, France. sebastien.lenglet@univ-rouen.fr
Louiset
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E
Delarue
C
C
Vaudry
H
H
Contesse
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D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000067956:Adenylyl Cyclase Inhibitors; D000450:Aldosterone / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020747:Calcium Channels, T-Type / Q000187:drug effects / Q000502:physiology*; D000242:Cyclic AMP / Q000096:biosynthesis; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D007546:Isoquinolines / Q000494:pharmacology; D020748:Mibefradil / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D051381:Rats; D011985:Receptors, Serotonin / Q000502:physiology*; D012701:Serotonin / Q000008:administration & dosage / Q000494:pharmacology*; D015398:Signal Transduction / Q000502:physiology; D013449:Sulfonamides; D015384:Zona Glomerulosa / Q000166:cytology / Q000502:physiology*
D000067956:Adenylyl Cyclase Inhibitors; D002121:Calcium Channel Blockers; D020747:Calcium Channels, T-Type; D004791:Enzyme Inhibitors; D007546:Isoquinolines; D011985:Receptors, Serotonin; D013449:Sulfonamides; C104425:serotonin 7 receptor; C017759:9-(tetrahydro-2-furyl)-adenine; D020748:Mibefradil; D012701:Serotonin; D000450:Aldosterone; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000225:Adenine; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D002118:Calcium