Activation of 5-hydroxytryptamine4 receptors causes calcium influx in adrenocortical cells: involvement of calcium in 5-hydroxytryptamine-induced steroid secretion.
5-Hydroxytryptamine (5-HT) stimulates corticosteroid secretion from adrenal cells through activation of 5-HT4 receptors positively coupled to adenylyl-cyclase. In the present study, we investigated in frog adrenocortical cells the effect of 5-HT4 receptor agonists on cytosolic calcium concentration ([Ca2+]i) and determined the sequence of events associated with 5-HT4 receptor agonist zacopride (10[-8] to 10[-5]M each in the vicinity of cultured adrenocortical cells caused a dose-dependent increase in [Ca2+]i. Preincubation of the cells with the selective 5-HT4 receptor antagonist [1-[2-(methylsulfonylamino)ethyl]-4- piperidinyl]methyl-1-methyl-1H-indole-3-carboxylate maleate totally blocked the 5-HT-induced stimulation of [Ca2+]i. Chelation of extracellular calcium with ethylene glycol bis (beta-aminoethyl ether)-N,N,N', N'-tetraacetic acid (10 MM) suppressed the stimulatory effect of 5-HT on [Ca2+]i. Conversely, thapsigargin, an inhibitor of calcium ATPase activity, had no effect on the [Ca2+]i rise. The calcium influx induced by 5-HT4 receptor agonists was not affected by nifedipine and omega-conotoxin GVIA but was totally blocked by pimozide, a T-type calcium channel antagonist. The [Ca2+]i response to zacopride was potentiated by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine and markedly reduced by the protein kinase A inhibitor adenosine-3',5'-cyclic monophosphorothioate. We studied in perifused frog adrenal slices the involvement of [Ca2+]i rise and cAMP formation in the mechanism of action of 5-HT4 receptor agonists. Zacopride-induced steroidogenesis was significantly reduced in the presence of adenosine-3'5'-cyclic monophosphorothioate or after suppression of calcium in the perifusion medium. The stimulatory effect of zacopride on corticosteroid secretion was not affected by nifedipine and omega-conotoxin GVIA but was significantly inhibited by pimozide. Taken together, these data indicate that activation of 5-HT4 receptors in adrenocortical cells causes stimulation of adenylyl cyclase and subsequently increases calcium influx through a T-type calcium channel. Both the increased in cAMP formation and the calcium rise are involved in the stimulatory effect of 5-HT on corticosteroid secretion.
Contesse
V
V
Laboratory of Cellular and Molecular Neuroendocrinology, INSERM U 413, University of Rouen, Mont-Saint-Aignan, France.
Hamel
C
C
Lefebvre
H
H
Dumuis
A
A
Vaudry
H
H
Delarue
C
C
D000302:Adrenal Cortex / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D000305:Adrenal Cortex Hormones / Q000378:metabolism*; D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000502:physiology; D007211:Indoles / Q000494:pharmacology; D008297:Male; D011895:Rana ridibunda; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology
D000305:Adrenal Cortex Hormones; D001549:Benzamides; D019086:Bridged Bicyclo Compounds, Heterocyclic; D007211:Indoles; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D013449:Sulfonamides; D012701:Serotonin; C055971:zacopride; D000242:Cyclic AMP; D002118:Calcium; C082871:GR 113808