Basal and stretch-augmented natriuretic peptide secretion by quiescent rat atria.
Absolute rates of immunoreactive atrial natriuretic peptide (ANP) secretion were measured in vitro at 37 degrees C in noncontracting preparations of combined right and left rat atria at constant distending pressures of 0 or 5.1 mmHg in presence of 0.2 mM extracellular Ca2+ concentration [( Ca2+]o), 10 microM ryanodine, and either 1 microM saxitoxin or 10 microM tetrodotoxin. By systematic deletion of external Na+, K+, Mg2+, Cl-, or HCO3-, and reduction of [Ca2+]o, and by selective ion transport inhibitors, neither net transplasmalemmal fluxes of Na+, Cl-, HCO3-, and Mg2+ nor ryanodine-sensitive Ca2+ release from sarcoplasmic reticulum (SR) was found necessary for stretch augmentation of secretory rate (Ra). Ra 1) was near zero within 20 min when extracellular Na+ concentration = 0 and [Ca2+]o = 20 microM and within 5 min or less after preincubation with caffeine, 8-chlorophenylthioadenosine 3',5'-cyclic monophosphate, or at 18 degrees C; 2) was significantly decreased by Cd2+, Ni2+, the isoquinoline H-7, and trifluoperazine but not 100 microM ryanodine; 3) was increased by neomycin; and 4) had an apparent activation energy of 18.5 +/- 4.1 x 10(3) cal/mol between 23 and 42 degrees C. These experiments strongly implicated transplasmalemmal Ca2+ influx and cAMP but not SR Ca2+ release in control of Ra under the experimental conditions studied.
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Department of Medicine, University of Chicago, Illinois 60637.
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Upshaw-Earley
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D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D016275:Atrial Function; D009320:Atrial Natriuretic Factor / Q000378:metabolism*; D002104:Cadmium / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D005260:Female; D006321:Heart / Q000502:physiology*; D006325:Heart Atria / Q000187:drug effects / Q000648:ultrastructure; D066298:In Vitro Techniques; D007700:Kinetics; D008854:Microscopy, Electron; D009200:Myocardial Contraction; D051381:Rats; D011919:Rats, Inbred Strains; D012433:Ryanodine / Q000494:pharmacology; D012530:Saxitoxin / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D013816:Thermodynamics
D002121:Calcium Channel Blockers; D002104:Cadmium; D012433:Ryanodine; D012530:Saxitoxin; D013779:Tetrodotoxin; D000584:Amiloride; D009320:Atrial Natriuretic Factor