Vasopressin and protein kinase A activate G protein-sensitive epithelial Na+ channels.
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 (2-56%). Addition of the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine, the adenosine 3',5'-cyclic monophosphate (cAMP) analogues, 8-(4-chlorophenylthio)-cAMP and 8-bromo-cAMP, or forskolin elicited a comparable effect to that of AVP. The induced channels had similar properties 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 ng/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.
Renal Unit, Massachusetts General Hospital, Charlestown 02129.
A G
AG
Prat
D A
DA
Ausiello
H F
HF
Cantiello
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D002460:Cell Line; D000242:Cyclic AMP / Q000494:pharmacology; D004594:Electrophysiology; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology*; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D037342:Pertussis Toxin; D011494:Protein Kinases / Q000494:pharmacology*; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D015222:Sodium Channels; D010566:Virulence Factors, Bordetella; D001127:Arginine Vasopressin; D000584:Amiloride; D000242:Cyclic AMP; D037342:Pertussis Toxin; D011494:Protein Kinases; D019204:GTP-Binding Proteins