Ej. Kelso et al., Endothelin, receptor subtype mediates endothelin-induced contractility in left ventricular cardiomyocytes isolated from rabbit myocardium, J PHARM EXP, 294(3), 2000, pp. 1047-1052
Citations number
35
Categorie Soggetti
Pharmacology & Toxicology
Journal title
JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS
Endothelin (ET)-1 is a potent positive inotropic agent, the effects of whic
h are mediated by increases in cytosolic Ca2+ in the myocardium. The object
of this study was to examine 1) the influence of ETA and ETB receptor subt
ypes, and 2) the role of the phospholipase C (PLC) pathway in mediating ET-
1-induced contraction. Left ventricular cardiomyocytes were isolated from t
he hearts of New Zealand White rabbits (2-2.5 kg) by the use of Langendorff
perfusion with collagenase. Cardiomyocyte function was examined during unl
oaded, electrically stimulated (0.5 Hz) contractions with a video-edge dete
ction system. ET-1 increased cell shortening with greater potency than ET-3
: mean EC50 values were 1.1 x 10(-11) and 2.6 x 10(-10) M, respectively. Wi
th the same order of potency, ET-1 and ET-3 increased (P < .05) velocity of
cell shortening. The ETA receptor-selective antagonist ABT-627 shifted the
ET-1-induced cell shortening response curve to the right with a pA(2) valu
e of 10.3. The ETB receptor-selective antagonist A-192621 (10(-8)-10(-7) M)
did not alter the concentration-response of ET-1. Moreover, the ETB recept
or-selective agonist sarafotoxin 6c did not have any effect on cell shorten
ing over the concentration range of 10(-11) to 10(-7) M. ET-1 in the presen
ce of the PLC inhibitor U-73122 did not alter the contractile amplitude. Ho
wever, ET-1 in the presence of the protein kinase C inhibitor bisindolylmal
emide increased cell shortening. These findings indicate that 1) the ETA re
ceptor subtype, and not the ETB receptor subtype, mediates the positive ino
tropic effect of ET-1, acid 2) the response of ET-1 is mediated by a PLC pa
thway, but not through protein kinase C, in ventricular cardiomyocytes isol
ated from rabbit myocardium.