Characterization of vasopressin-induced calcium mobilization in CHO cells transfected rat V_1a receptor

• Published in: Japanese Journal of Pharmacology Vol. 67; no. suppl.1; p. 87
• Main Authors: Michio Takeda, Keiji Maekawa, Yoshikuni Onodera, Hitoshi Endou
• Format: Journal Article
• Language: Japanese
• Published: The Japanese Pharmacological Society 1995
• ISSN: 0021-5198

The purpose of this study is to investigate the mechanism for arginine vasopressin (AVP) -induced calcium mobilization in Chinese hamster ovary (CHO) cells stably expressing rat V_1a receptor (CHO V_1a cells). The presence of V_1a receptor was confirmed by saturable ligand binding studies. Intracellular calcium concentration (「Ca^2+ 」_i ) was measured using fura-2/AM. AVP induced a biphasic increase in 「Ca^2+ 」_i , which consists of an initail transient and ensuing sustained plateau. AVP-induced transient increase in 「Ca^2+ 」_i occured in a dose-dependent manner in the range between 10^-5 M and 10^-11 M. AVP-induced 「Ca^2+」i increase was inhibited by 「d(CH_2 )_5 Tyr(Me)AVP」 (V_1a antagonist), but affected little by 「d(CH_2 )_5 , D-ILe^2 ,ILe^4 -AVP」 (V_2 antagonist). The second plateau increase but not the initial transient increase in 「Ca^2+」_i induced by AVP was suppressed by removal of extracellular Ca^2+ and the pretreatment of verapamil and nicardipine, but not diltiazem. AVP-induced 「Ca^2+ 」_i increase was inhibited by pretreatment of the cells with neomycin and pertussis toxin, suggesting the V_1a receptor is coupled to phospholipase C via pertussis toxin-sensitive G protein. In summary, we showed that vasopressin-induced calcium mobilization in CHO V_1a cells occurs in a manner analogous to that observed in native tissues. Thus, CHO V_1a cells may provide a valuable tool for investigating further the transmenbrane and intracellular signaling pathways leading to calcium mobilization and studying the functional activities of AVP receptor antagonists.