Effects of prostaglandin E2 on amiloride-blockable Na+ channels in a distal nephron cell line (A6).
We studied the mechanisms by which prostaglandin E2 (PGE2) regulates amiloride-blockable 4-pS Na+ channels in A6 distal nephron cells. With each apical cell-attached patch acting as its own control, acute (3-6 min) basolateral, but not apical, exposure to 1 microM PGE2 inhibited Na+ channel activity by decreasing the open probability (Po). This PGE2-induced inhibition was attenuated by 30 min pretreatment with the protein kinase C (PKC) antagonists 1 microM staurosporine or 100 microM D-sphingosine but was insensitive to pertussis toxin (PTX). Furthermore, the time course for channel inhibition by acute PGE2 correlated with a transient increase in intracellular inositol 1,4,5-trisphosphate (IP3) levels. In contrast, after chronic (10-50 min) exposure of A6 cells to 1 microM basolateral PGE2, channel activity was stimulated compared with controls. This stimulation was due to an increase in the number of apical Na+ channels, similar to the effect of maneuvers that increase intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels in A6 cells (22). Indeed, chronic exposure to basolateral PGE2 correlated with a sustained increase in cAMP levels. In conclusion, 1) the regulation of apical 4-pS highly selective Na+ channel activity by basolateral PGE2 is a complicated biphasic process, which includes inhibition by acute PGE2 and stimulation by chronic PGE2 exposure; 2) acute PGE2 promotes a transient generation of IP3 which activates Ca(2+)-dependent PKC and promotes a decrease in Po; 3) chronic PGE2 promotes a sustained generation of cAMP that leads to an increase in channel density; and 4) both the acute and chronic effects of PGE2 on Na+ channels are PTX-insensitive processes.
Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.
K E
KE
Kokko
P S
PS
Matsumoto
B N
BN
Ling
D C
DC
Eaton
D000262:Adenylyl Cyclases / Q000378:metabolism; D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D015232:Dinoprostone / Q000494:pharmacology*; D019204:GTP-Binding Proteins / Q000502:physiology; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D009399:Nephrons / Q000166:cytology / Q000378:metabolism*; D037342:Pertussis Toxin; D011493:Protein Kinase C / Q000378:metabolism; D026941:Sodium Channel Blockers; D015222:Sodium Channels / Q000187:drug effects* / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D026941:Sodium Channel Blockers; D015222:Sodium Channels; D010566:Virulence Factors, Bordetella; D000584:Amiloride; D015544:Inositol 1,4,5-Trisphosphate; D000242:Cyclic AMP; D037342:Pertussis Toxin; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D015232:Dinoprostone