Influence of heart rate on the effects of prenalterol on regional myocardial blood flow and function during coronary stenosis in dogs.

Abstract

The effects of prenalterol, a selective beta 1-adrenoceptor agonist with potent cardiac positive inotropic properties have been investigated on regional myocardial blood flow (RMBF) (microspheres) and contractile function (ultrasonic crystals) during partial circumflex coronary artery stenosis in 8 open-chest anaesthetized dogs. Prenalterol was investigated at two intravenous doses: 5 micrograms kg-1, which increased myocardial contractility (dP/dt max: +29%) more than heart rate (+12%, up to 150 beats min-1) and 20 micrograms kg-1 which induced almost similar increases in contractility (+35%) and heart rate (+31% up to 175 beats min-1). The induced modifications of regional flow and function were then compared to those produced in another series of 6 dogs by atrial pacing at 150 and 175 beats min-1 respectively. Prenalterol significantly increased RMBF and segment length (SL)-shortening in a dose-dependent manner in the nonischaemic zone. In the ischaemic zone, RMBF was maintained and SL-shortening increased with prenalterol, 5 micrograms kg-1 whereas both RMBF and contractile function were severely decreased with prenalterol, 20 micrograms kg-1. Atrial pacing had almost no effect on RMBF and SL-shortening in the nonischaemic zone. In the ischaemic zone, atrial pacing rate-dependently decreased both RMBF and SL-shortening. Thus, a significant increase in contractility, associated with little tachycardia (prenalterol, 5 micrograms kg-1), induces beneficial effects on RMBF and function in both the nonischaemic and ischaemic myocardium. In contrast, a strong tachycardia, whether accompanied by positive inotropic effects (prenalterol, 20 gig kg-') or not (atrial pacing at 175 beats min-1) induces deleterious effects on RMBF and cardiac function in the ischaemic myocardium.

• Authors: A Berdeaux, C Bonhenry, P Duhazé, J F Giudicelli, C Thuillez
• Journal: British journal of pharmacology (Br J Pharmacol) Vol. 83 Issue 1 Pg. 203-10 (Sep 1984) ISSN: 0007-1188 [Print] England
• PMID: 6148979 (Publication Type: Journal Article)

Chemical References

• Adrenergic beta-Agonists
• Prenalterol
• Practolol

Topics

• Adrenergic beta-Agonists (pharmacology)
• Animals
• Cardiac Output (drug effects)
• Cardiac Pacing, Artificial
• Coronary Circulation (drug effects)
• Coronary Disease (physiopathology)
• Dogs
• Female
• Heart Rate
• Male
• Myocardial Contraction (drug effects)
• Practolol (analogs & derivatives, pharmacology)
• Prenalterol
• Time Factors