Electrophysiological study of luminal and basolateral vasopressin in rabbit cortical collecting duct

To clarify the mechanism of action of arginine vasopressin (AVP) on ionic conductances, electrophysiological technique was applied to the rabbit cortical collecting duct (CCD) perfused in vitro. When AVP (100 pM) was added to the bath, transepithelial voltage (VT), transepithelial resistance (RT), and fractional resistance of the apical membrane (fRA) of the principal cell displayed biphasic responses: initial increase in lumen-negative VT (phase I) was associated with decreases in RT and fRA, whereas secondary decrease in VT (phase II) was associated with increases in RT and fRA. In phase I, depolarization of the luminal membrane was observed due to stimulation of Na+ conductance in the luminal membrane. In phase II, mixed responses of both hyperpolarization of the luminal membrane, due to late inhibition of Na+ conductance, and depolarization of the basolateral membrane, due to stimulation of Cl- conductance, were observed. 8-(4-Chlorophenylthio)-adenosine 3',5'-cyclic monophosphate, as a pure vascular AVP receptor 2 (V2) action, mimicked the actions of AVP. Addition of AVP (100 pM to 1 nM) in the lumen resulted in increases in lumen-negative VT and RT. Luminal AVP did not affect the electrical parameters in beta-intercalated cells. In principal cells, luminal AVP caused sustained increase in total membrane resistance (Ri), together with an initial depolarization of the luminal membrane followed by a late hyperpolarization of the basolateral membrane. Because the initial response was abolished in the presence of 2 mM Ba2+ in the lumen, an inhibition of luminal K+ conductance may be responsible for the initial phase of luminal AVP action. Late hyperpolarization of the basolateral membrane associated with an increase in membrane resistance was abolished in the absence of ambient Cl-. Under the condition where Cl- conductance of the basolateral membrane was stimulated by administration of cAMP in the bath, voltage deflections of the basolateral membrane on changing Cl- concentration in the bath from 120 to 12 mM decreased by 88% in the presence of luminal AVP. These observations are in accord with the view that the basolateral Cl- conductance was inhibited by luminal AVP in the later phase. These data indicate that AVP in the lumen inhibits basolateral Cl- conductance, which is stimulated by AVP in the bath.