Inhibition of epithelial Na+ transport by atriopeptin protein kinase C and pertussis toxin.

MATTHIAS MOHRMANN, HORACIO F. CANTIELLO, AND DENNIS A. AUSIELLO

AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY

Año: 1987 p. 372 - 376

0363-6143

We have recently shown the selective inhibition of an amiloride- sensitive, conductive pathway for Na’ by atria1 natriuretic peptide and 8-bromoguanosine 3’,5’ -cyclic monophosphate (SBrcGMP) in the renal epithelial cell line, LLC-PK,. Using ‘“Na’ fluxes, we further investigated the modulation of Na’ transport by atria1 natriuretic peptide and by agents that increase cGMP production, activate protein kinase c, or modulate guanine nucleotide regulatory protein function. Sodium nitroprusside increases intracellular cGMP concentrations without affecting CAMP concentrations and completely inhibits amiloride- sensitive Na” uptake in a time- and concentration-dependent manner. In contrast, 8-BrcAMP is without effect on Na+ uptake through the Na” channel. 1-Qleoyl2-acetylglycerol (10 pg/ml) and phorbol 1%myristate 13-acetate (100 nM), activators of protein kinase c, inhibit Na+ uptake by 93 t 13 and 51 t lo!%, respectively. Prolonged incubation with phorbol ester results in t,he downregulation of protein kinase 4: activity and reduces the inhibitory effect of atria1 natriuretic peptide, suggesting that the action of this peptide involves stimulation of protein kinase c. Pertussis toxin, which induces the ADPribosylation of a 41-kDa guanine nucleotide regulatory protein in LLC-PK, cells, inhibits “Na+ influx to the same extent as amiloride. Thus, increasing cGMP, activating protein kinase c, and ADP-ribosylating a guanine nucleotide regulatory protein all inhibit Na’ uptake. These events may be sequentially involved in the action of atria1 natriuretic peptide.