RT Journal Article
SR Electronic
T1 Characterization of the beta adrenoceptor subtype(s) mediating the positive inotropic effects of epinine, dopamine, dobutamine, denopamine and xamoterol in isolated human right atrium.
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 532
OP 538
VO 262
IS 2
A1 N M Deighton
A1 S Motomura
A1 S Bals
A1 H R Zerkowski
A1 O E Brodde
YR 1992
UL http://jpet.aspetjournals.org/content/262/2/532.abstract
AB In patients with chronic heart failure cardiac beta-1 adrenoceptors are reduced, whereas beta-2 adrenoceptor changes vary depending on the etiology of the disease. Beta Adrenoceptor agonists can be used for short-term inotropic support in chronic heart failure; their clinical efficacy might depend on which beta adrenoceptor subtype(s) mediates their positive inotropic effect. Thus, the beta adrenoceptor subtype(s) involved in the positive inotropic effects of clinically used beta adrenoceptor agonists was characterized on isolated electrically driven human right atria by the use of the selective beta-1 adrenoceptor antagonist CGP 20712 A (300 nmol/l) and/or the selective beta-2 adrenoceptor antagonist ICI 118,551 (30 nmol/l). Epinine evoked positive inotropic effects through stimulation of beta-1 and beta-2 adrenoceptors to about the same degree, whereas dobutamine acted mainly at beta-1 adrenoceptors but had a significant beta-2 adrenoceptor component. Both agonists were full agonists causing the same maximum increase in contractile force (Emax) as did isoprenaline or Ca++ (Emax = 1.0). In contrast, denopamine was a partial selective beta-1 adrenoceptor agonist (Emax = 0.75-0.85). Dopamine was in the presence of uptake1-blockade (by 5 mumol/l phenoxybenzamine) a partial agonist (Emax = 0.60-0.70) acting selectively at beta-1 adrenoceptors; in the absence of uptake1-blockade, however, dopamine was a full agonist, indicating that part of its positive inotropic effect is indirect via the release of endogenous noradrenaline. Xamoterol did not exert positive inotropic effects, but concentration-dependently slightly decreased basal force of contraction.