Alpha-adrenoceptors and alpha-adrenoceptor-mediated positive inotropic effects in failing human myocardium.

Abstract

Experiments were designed to characterize cardiac alpha-adrenoceptors and the alpha-adrenoceptor-mediated positive inotropic effects in human myocardial tissue from patients with moderate New York Heart Association (NYHA) class II-III and severe (NYHA class IV) heart failure. The number of cardiac alpha-adrenoceptors was low but similar in moderate and severe heart failure (NYHA class II-III: 6.7 +/- 0.8 fmol/mg protein 3H-prazosin bound, n = 12; NYHA class IV: 7.4 +/- 0.9 fmol/mg protein 3H-prazosin bound, n = 9; NS). Correspondingly, the alpha-adrenoceptor-mediated positive inotropic effect (phenylephrine in the presence of propranolol) did not significantly differ in both groups. In the same hearts, the number of beta-adrenoceptors was measured. The number of beta-adrenoceptors was significantly reduced in severe heart failure (NYHA class II-III: 22.0 +/- 1.5 fmol/mg protein 3H-CGP 12177 bound, n = 12; NYHA class IV: 11.9 +/- 0.8 fmol/mg protein 3H-CGP 12177 bound, n = 9; p less than 0.05). The positive inotropic effect of isoprenaline was significantly reduced in NYHA class IV. The positive inotropic effect of Ca2+ was similar in both groups. In conclusion, cardiac beta-adrenoceptors and the beta-adrenoceptor-mediated positive inotropic effects were reduced in severely failing myocardium. Cardiac alpha-adrenoceptors and the positive inotropic effect resulting from their stimulation is unchanged. Therefore, down regulation in response to increased sympathetic stimulation or a compensatory increase of alpha-adrenoceptors does obviously not occur in the human heart.(ABSTRACT TRUNCATED AT 250 WORDS)

• Authors: M Böhm, F Diet, G Feiler, B Kemkes, E Erdmann
• Journal: Journal of cardiovascular pharmacology (J Cardiovasc Pharmacol) Vol. 12 Issue 3 Pg. 357-64 (Sep 1988) ISSN: 0160-2446 [Print] United States
• PMID: 2464110 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Receptors, Adrenergic, alpha
• Receptors, Adrenergic, beta
• Phenylephrine
• Isoproterenol
• Calcium

Topics

• Adult
• Aged
• Calcium (pharmacology)
• Female
• Heart Failure (physiopathology)
• Humans
• In Vitro Techniques
• Isoproterenol (pharmacology)
• Male
• Middle Aged
• Myocardial Contraction (drug effects)
• Papillary Muscles (metabolism)
• Phenylephrine (pharmacology)
• Receptors, Adrenergic, alpha (physiopathology)
• Receptors, Adrenergic, beta (drug effects, metabolism)