A low affinity, low molecular weight endothelin-A receptor present in neonatal rat heart.
1. Addition of endothelin-1 (ET-1) to [3H]-inositol-labelled neonatal rat hearts stimulated the accumulation of [3H]-labelled inositol phosphates (InsP), but only at high concentrations; concentration at half maximum stimulation (EC50) > 0.1 mumol/L). When similar experiments were performed using isolated myocytes, the potency of endothelin-1 was higher and the EC50 value averaged 3.2 +/- 0.5 nmol/L (mean +/- s.e.m., n = 4). 2. The binding affinity of [125I]-endothelin-1 was higher for receptors on isolated cells than for receptors on membranes prepared from intact heart (72 +/- 16 pmol/L compared with 3.9 +/- 0.7 nmol/L, mean +/- s.e.m., n = 4, P < 0.01; Students' t test). 3. Receptors from both sources were cross-linked to [125I]-endothelin-1 and their molecular weights measured using sodium dodecylsulfate gradient polyacrylamide gel electrophoresis (SDS-PAGE). The receptors present on the isolated cells had a higher molecular weight (48 kD) than the receptor on the heart membranes (38 kD).
Woodcock
E A
EA
Cellular Biochemistry Laboratory, Baker Medical Research Institute, Prahran, Victoria, Australia.
Land
S L
SL
Andrews
R K
RK
D000818:Animals; D000831:Animals, Newborn; D001665:Binding Sites; D002469:Cell Separation; D016232:Endothelins / Q000378:metabolism / Q000494:pharmacology; D006321:Heart / Q000187:drug effects*; D007295:Inositol Phosphates / Q000378:metabolism; D008970:Molecular Weight; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017466:Receptors, Endothelin / Q000378:metabolism*
D016232:Endothelins; D007295:Inositol Phosphates; D017466:Receptors, Endothelin