Vasotocin has the potential to inhibit basolateral Na(+)/K (+)-pump current across isolated skin of tree frog in vitro, via its V(2)-type receptor/cAMP pathway.
Adult frog skin transports Na(+) from the apical to the basolateral side across the skin. Antidiuretic hormone (ADH) is involved in the regulation of Na(+) transport in both mammals and amphibians. We investigated the effect of arginine vasotocin (AVT), the ADH of amphibians, on the short-circuit current (SCC) across intact skin and on the basolateral Na(+)/K(+)-pump current across apically nystatin-permeabilized skin of the tree frog, Hyla japonica, in which the V(2)-type ADH receptor is expressed in vitro. In intact skin, 1 pM AVT had no effect on the SCC, but 10 nM AVT was sufficient to stimulate the SCC since 10 nM and 1 microM of AVT increased the SCC 3.2- and 3.4-fold, respectively (P > 0.9). However, in permeabilized skin, AVT (1 microM) decreased the Na(+)/K(+)-pump current to 0.79 times vehicle control. Similarly, 500 microM of 8Br-cAMP increased the SCC 3.2-fold, yet 1 mM of 8Br-cAMP decreased the Na(+)/K(+)-pump current to 0.76 times vehicle control. Arachidonic acid (10(-5) M) tended to decrease the Na(+)/K(+)-pump current. To judge from these in vitro experiments, AVT has the potential to inhibit the basolateral Na(+)/K(+)-pump current via the V(2)-type receptor/cAMP pathway in the skin of the tree frog.
Department of Physiology, School of Medicine, Saitama Medical University, Moroyama, Iruma-gun, Saitama 350-0495, Japan. makokam@saitama-med.ac.jp
Makoto
M
Takada
Kayo
K
Fujimaki
Shigeru
S
Hokari
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D001001:Anura / Q000378:metabolism*; D016718:Arachidonic Acid / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D007476:Ionophores / Q000494:pharmacology; D008564:Membrane Potentials; D009761:Nystatin / Q000494:pharmacology; D010539:Permeability; D017483:Receptors, Vasopressin / Q000378:metabolism*; D012867:Skin / Q000187:drug effects / Q000201:enzymology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013997:Time Factors; D014668:Vasotocin / Q000378:metabolism*
D007476:Ionophores; D017483:Receptors, Vasopressin; C034862:vasotocin receptor; D009761:Nystatin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D016718:Arachidonic Acid; D000242:Cyclic AMP; D000254:Sodium-Potassium-Exchanging ATPase; D014668:Vasotocin