Endothelin receptors in adult human and swine isolated ventricular cardiomyocytes.
The present study aimed to investigate endothelin-1 (ET-1) receptors in human and swine cardiomyocytes with binding studies using ET(A) and ET(B) selective receptor antagonists (BMS-182874 and BQ-788, respectively). Cell distribution of mRNA expression for ET(A) and ET(B) subtypes was investigated by in situ hybridization using specific cDNA probes. The 1251-ET-1 binding, which reached equilibrium in about 120 min (Kobs = 0.051+/-0.003 min(-1)), was only partially displaceable by the addition of a large excess of ET-1 (about 15% with a half-life of 20 min). In equilibrium binding studies, 125I-ET-1 had a Kd of 0.43+/-0.08 nM and a maximum binding (Bmax) of 42.8+/-6.6 fmol/mg protein. ET(A) and ET(B) receptors are represented in human and swine cardiomyocytes with an 85:15 ratio as indicated by the biphasic pattern of competition of both BMS-182874 and BQ-788. In situ hybridization studies confirmed that myocytes mainly expressed mRNA for ET(A), whereas expression of mRNA for the ET(B) subtype was documented in non-myocyte cells. These results showed that ET-1 binds with high affinity and poor reversibility to specific receptors, in both human and swine isolated ventricular cardiomyocytes, without significant species differences.
Modesti
P A
PA
Clinica Medica e Cardiologia, University of Florence, Italy. pa.modesti@dfc.unifi.it
Vanni
S
S
Paniccia
R
R
Perna
A
A
Maccherini
M
M
Lisi
G
G
Sani
G
G
Neri Serneri
G G
GG
D000328:Adult; D000818:Animals; D001667:Binding, Competitive; D065128:Endothelin Receptor Antagonists; D006352:Heart Ventricles / Q000378:metabolism; D006801:Humans; D017403:In Situ Hybridization; D007700:Kinetics; D008875:Middle Aged; D009206:Myocardium / Q000378:metabolism*; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000378:metabolism*; D013552:Swine; D016277:Ventricular Function, Left
D065128:Endothelin Receptor Antagonists; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin