Effects of arginine vasotocin and vasopressin receptor antagonists on Na super(+) and Cl super(-) transport in the isolated skin of two frog species, Hyla japonica and Rana nigromaculata

• Published in: General and comparative endocrinology 2008-05, Vol.157 (1), p.63-69
• Main Authors: Yamada, T, Nishio, T, Sano, Y, Kawago, K, Matsuda, K, Uchiyama, M
• Format: Article
• Language: English
• Subjects: Freshwater; Hyla japonica; Rana nigromaculata
• ISSN: 0016-6480
• DOI: 10.1016/j.ygcen.2008.03.022

Physiological function of arginine vasotocin (AVT) and effect of receptor antagonists of vasopressin were electrophysiologically investigated on transepithelial transport of ions in the abdominal skin of Hyla japonica and Rana nigromaculata by means of the Ussing chamber system. Administrations of AVT and forskolin (adenylate cyclase activator) in the serosal side of normal Ringer's solution significantly increased transepithelial potential difference (PD) and short-circuit current (Isc) accounting for Na super(+) influx, mucosal to serosal direction, across the skin of H. japonica. In contrast, AVT administrations significantly decreased PD but not Isc on the skin of R. nigromaculata in a concentration-dependent manner ranging from 10 super(-) super(1) super(1) to 10 super(-) super(8)M. Administration of 10 super(-) super(5)M forskolin also significantly decreased PD in normal and low Na super(+) Ringer's solution and in the presence of amiloride (Na super(+) channel blocker) on the mucosal side of normal Ringer's solution. On the other hand, forskolin significantly increased PD and Isc in the Cl super(-) free Ringer's solution. These results suggested that AVT and forskolin stimulated mainly Cl super(-) influx across the skin of R. nigromaculata. In two frog species, the AVT actions on ion transports were inhibited by pretreatment of OPC-31260 (a vasopressin V sub(2) receptor antagonist) but not OPC-21268 (a vasopressin V sub(1) receptor antagonist). These results suggested that AVT activates adenylate cyclase via V sub(2)-like receptor and stimulates actively net Na super(+) and net Cl super(-) transports in the abdominal skin of H. japonica and R. nigromaculata, respectively.