Vasopressin and protein kinase A activate G protein-sensitive epithelial Na+ channels

ADRIANA G. PRAT, DENNIS A. AUSIELLO, AND HORACIO F. CANTIELLO

AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY

Año: 1993 p. 218 - 223

0363-6143

To determine the molecular steps involved in the vasopressin-induced renal Na+ reabsorption, the patch-clamp technique was utilized to study the role of this hormone in the regulation of apical Na+ channels in renal epithelial A6 cells. Addition of arginine vasopressin (AVP) induced and/or enhanced Na+ channel activity within 5 min of addition under cell-attached conditions. The AVP-induced channel activity was a reflection of both an increase in the average apparent channel number (0.2-1.7) and the percent open time (256%). Addition of the phosphodiesterase inhibitor, 3-isobutyl-I-methylxanthine, the adenosine 3’,5’-cyclic monophosphate (CAMP) analogues, 8-(4-chlorophenylthio)- CAMP and &bromo-CAMP, or forskolin elicited a comparable effect to that of AVP. The induced channels had similar propertie to Na+ channels previously reported, including a channel conductance of 9 pS, Na+-to-K+ selectivity of 3-5:1, and high amiloride sensitivity. The CAMP-dependent protein kinase A (PKA) in the presence of ATP induced and/or enhanced Na+ channel activity in excised inside-out patches with a change in average apparent channel number and percent open probability similar to those observed with either AVP or CAMP analogues in intact cells. Addition of activated pertussis toxin (100 rig/ml) completely blocked the AVP- or PKA-induced Na+ channel activity in excised inside-out patches, whereas incubation of intact cells with the toxin completely prevented the effect of both activators. The data indicate that AVP mediates its effect through a CAMP-dependent pathway involving PKA activation whose target is the G protein pathway that regulates apical epithelial Na+ channel activity.