title: Distinct receptor subtypes mediate arginine vasopressin-dependent ACTH release and intracellular calcium mobilization in rat pituitary cells.
abstract: In the present study, adrenocorticotropic hormone (ACTH) release and intracellular calcium ([Ca(2+)](i)) increase induced by arginine vasopressin (AVP) were characterized in collagenase-dispersed and 3-day cultured rat anterior pituitary cells. AVP and the selective vasopressin V(1b) receptor agonist, [1-deamino-4-cyclohexylalanine]AVP (d[Cha(4)]AVP) induced ACTH release with nanomolar potencies in both cell preparations, and produced a maximal stimulation that was about 1.5 fold greater in the 3-day cultured cells, indicating that the vasopressin V(1b) receptor-ACTH release pathway is enhanced over time in culture. In dispersed cells, AVP, oxytocin and d[Cha(4)]AVP induced [Ca(2+)](i) increases with nanomolar potencies. The selective vasopressin V(1a) receptors antagonist, SR49059 (100 nM), together with the selective oxytocin receptors antagonist (d(CH(2))(5)(1)Tyr(Me)(2),Thr(4),Orn(8),Tyr-NH(2)(9)-vasotocin (100 nM), inhibited the maximal AVP response by ~70%, without affecting the response to d[Cha(4)]AVP, suggesting that the V(1b) receptor was only partially responsible for the AVP-induced [Ca(2+)](i) increase. In contrast, in 3-day cultures, AVP induced an increase in [Ca(2+)](i), while oxytocin and d[Cha(4)]AVP did not. The response to AVP was completely antagonized by SR49059, whereas the vasopressin V(1b) receptor antagonists, SSR149415 and (d(CH(2))(5)(1)Tyr(Me)(2),Thr(4),Orn(8),Tyr-NH(2)(9))-vasotocin had no effect, indicating that the [Ca(2+)](i) increase was mediated exclusively by vasopressin V(1a) receptors. In conclusion, the enhancement of vasopressin V(1b) receptor-mediated ACTH release and the lack of a detectable vasopressin V(1b) receptor coupling to [Ca(2+)](i) increase in cultured cells suggests the activation of a different/additional signaling pathway in the molecular mechanism of ACTH release.
authors.affiliation: Neurosciences Centre of Excellence for Drug Discovery, GlaxoSmithKline, 37135 Verona, Italy. Elisabetta.Perdona@aptuit.com
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Perdonà
authors.forename: Roberto
authors.initials: R
authors.lastname: Arban
authors.forename: Cristiana
authors.initials: C
authors.lastname: Griffante
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D065092:Antidiuretic Hormone Receptor Antagonists; D001127:Arginine Vasopressin / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D004347:Drug Interactions; D005260:Female; D007211:Indoles / Q000494:pharmacology; D010121:Oxytocin / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011759:Pyrrolidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017483:Receptors, Vasopressin / Q000819:agonists*; D013997:Time Factors; D014668:Vasotocin / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: C456029:1-(5-chloro-1-((2,4-dimethoxyphenyl)sulfonyl)-3-(2-methoxyphenyl)-2-oxo-2,3-dihydro-1H-indol-3-yl)-4-hydroxy-N,N-dimethyl-2-pyrrolidinecarboxamide; D065092:Antidiuretic Hormone Receptor Antagonists; D007211:Indoles; D011759:Pyrrolidines; D017483:Receptors, Vasopressin; C096587:vasotocin, d(CH2)5-O--methyl-Tyr(2)-Thr(4)-N(delta)-propionyl-Orn(8)-Tyr(9)-NH2; D001127:Arginine Vasopressin; D010121:Oxytocin; D000324:Adrenocorticotropic Hormone; C082134:relcovaptan; D000242:Cyclic AMP; D002118:Calcium; D014668:Vasotocin