RT Journal Article
SR Electronic
T1 Hydroxylated Chlorpromazine Metabolites: Positive Inotropic Action and the Release of Catecholamines
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 1076
OP 1085
VO 13
IS 6
A1 KYOSUKE TEMMA
A1 TAI AKERA
A1 THEODORE M. BRODY
A1 ALBERT A. MANIAN
YR 1977
UL http://molpharm.aspetjournals.org/content/13/6/1076.abstract
AB The mechanism of the positive inotropic action of the 7-mono- and 7,8-dihydroxylated metabolites of chlorpromazine was studied in isolated guinea pig hearts. In electrically driven left atrial preparations, these metabolites as well as 3,7,8-trihydroxychlorpromazine produced positive inotropic effects, which were prevented by prior treatment with either reserpine or propranolol. Although 7,8-dihydroxychlorpromazine is a potent inhibitor of (Na+ + K+)-ATPase in vitro, it failed to affect sodium pump activity in Langendorff preparations at the time of the positive inotropic effect, indicating that this compound cannot gain access to the site of inhibition on the sodium pump during the relatively short perfusion period. 7,8-Dihydroxychlorpromazine altered the transmembrane action potential configuration. These changes were similar to those produced by catecholamines. 7,8-Dihydroxychlorpromazine also increased the cyclic 3',5'-AMP concentration in atrial muscles, an effect that appeared to be related to the positive inotropic action. Both these effects were prevented by prior treatment with reserpine. In electrically driven left atrial preparations, 7,8-dihydroxychlorpromazine released previously loaded [3H]metaraminol without affecting its uptake. It is concluded the hydroxylated metabolites of chlorpromazine release catecholamines from cardiac sympathetic nerve terminals and increase myocardial contractile force.