Regulation of atrial natriuretic peptide-stimulated cGMP production in the inner medulla.
Studies were performed to examine the regulation of atrial natriuretic peptide- (ANP) stimulated guanylate cyclase in the the inner medulla. Primary cultures of rat inner medullary collecting tubular cells exposed to 10(-7) M ANP increased cGMP formation to 31.2 +/- 1.8 compared to the basal production of 2.1 +/- 0.6 fm/micrograms protein. This response did not appear to be transduced via a Gi protein, as preincubation with pertussis toxin did not alter the response to 10(-7) M ANP, and saponized cells exposed to 10 microM GTP gamma S did not enhance the response to ANP (77.3 +/- 5.9 vs. 86.7 +/- 6.3 g/micrograms). Likewise, changes in extracellular Ca2+ from 0.5 to 3.0 mM, decrements in intracellular Ca2+ with EGTA or increments in intracellular Ca2+ with ionomycin (5 microM) did not significantly alter the response to ANP. Neither activation of protein kinase A with forskolin (36.5 +/- 5.1) nor of protein kinase C with s,n-1,2-dioctanoylglycerol (33.2 +/- 2.5) altered the response to 10(-7) M ANP (32.2 +/- 3.3, NS). As the inner medullary environment was hypertonic, the effect of altering tonicity was studied. Cells grown for 48 hours in hypertonic media (600 mOsm/kg H2O) displayed enhanced response to 10(-8) and 10(-7) M ANP when osmolality was raised by either Na+ alone or in combination with urea, but not by urea alone. Our studies demonstrate that ANP-stimulated guanylate cyclase is insensitive to alterations in either intra- or extracellular Ca2+, is not subject to inhibition by protein kinase, and does not involve a pertussis-sensitive G protein.(ABSTRACT TRUNCATED AT 250 WORDS)
Berl
T
T
Department of Medicine, University of Colorado School of Medicine, Denver.
Mansour
J
J
Veis
J H
JH
D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000096:biosynthesis*; D019204:GTP-Binding Proteins / Q000378:metabolism; D007679:Kidney Medulla / Q000187:drug effects / Q000378:metabolism*; D009994:Osmolar Concentration; D011494:Protein Kinases / Q000378:metabolism
D009320:Atrial Natriuretic Factor; D011494:Protein Kinases; D019204:GTP-Binding Proteins; D006152:Cyclic GMP; D002118:Calcium