Regulation of ANP secretion by endothelin-1 in cultured atrial myocytes: desensitization and receptor subtype.
We examined endothelin-1 (ET-1) binding and ET-1-regulated atrial natriuretic peptide (ANP) secretion in primary cultures of adult rat atrial myocytes. ET-1 binding was analyzed as a reversible bimolecular reaction, with bimolecular association rate constant = 1.9 x 10(9) M-1.h-1, dissociation rate constant = 0.028 h-1, and a dissociation constant, calculated from these values = 0.015 nM. ET-1 increased ANP secretion with a one-half effective concentration (EC50) of 0.62 nM, which correlated with EC50 receptor occupancy under equivalent experimental conditions (0.75 nM). The secretory response rapidly desensitized (half-time = 10 min at 10 nM ET-1). The time courses for ET-1 binding, ET-1-stimulated secretion, and desensitization were all comparable. Recovery from desensitization was slow and paralleled the recovery of 125I-labeled ET-1 binding. The ETA receptor subtype-selective antagonist, BQ-123, inhibited 125I-ET-1 binding and ET-1-activated ANP secretion with high affinity, whereas the ETB-selective agonists, endothelin-3 and sarafotoxin S6c, inhibited binding with low affinity and did not effectively stimulate ANP secretion. We conclude that 1) ET-1 can stimulate ANP secretion by direct action on the atrial myocytes; 2) primary cultures of adult rat atrial myocytes express only the ETA receptor subtype; 3) the ANP secretory response to ET-1 desensitizes rapidly but recovers slowly; and 4) occupation of the ETA receptors by ET-1 initiates the unidirectional sequence of receptor activation, signal transduction, ANP secretion, and finally, desensitization.
Leite
M F
MF
Department of Medicine, University of Chicago, Illinois 60637.
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E
Ambler
S K
SK
D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism*; D002478:Cells, Cultured; D065128:Endothelin Receptor Antagonists; D016232:Endothelins / Q000378:metabolism / Q000494:pharmacology*; D006325:Heart Atria / Q000378:metabolism; D007457:Iodine Radioisotopes; D007700:Kinetics; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010456:Peptides, Cyclic / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017466:Receptors, Endothelin / Q000378:metabolism; D012044:Regression Analysis; D015290:Second Messenger Systems; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D065128:Endothelin Receptor Antagonists; D016232:Endothelins; D007457:Iodine Radioisotopes; D010456:Peptides, Cyclic; D017466:Receptors, Endothelin; D009320:Atrial Natriuretic Factor; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; C072247:cyclo(Trp-Asp-Pro-Val-Leu)