The effect of pindolol on myocardial release of inosine, hypoxanthine and lactate during pacing-induced angina
Kugler, G.
Journal of Pharmacology and Experimental Therapeutics 209(2): 185-189
1979
ISSN/ISBN: 0022-3565 PMID: 438993 Document Number: 142712
Myocardial uptake or release of the ATP catabolites, inosine and hypoxanthine and of lactate was calculated for metabolic evaluation of the efficacy of pindolol as an antianginal drug in patients. Inosine and hypoxanthine were assayed enzymatically after separation by a column chromatographic method in arterial and coronary venous blood during pacing-induced angina and after .beta.-adrenergic blockade produced by 0.4 mg i.v. of pindolol at identical paced heart rates. Calculated myocardial lactate production during angina (-37 .+-. 31%) diminished 15 min after pindolol during the 2nd pacing period (-4.1 .+-. 25%, P < 0.01). Coronary venous inosine values during angina (615 .+-. 300 nmol/l) decreased after pindolol (565 .+-. 220 nmol/l, P = N.S. ), the arterial values (470 .+-. 125 nmol/l per l) increased (655 .+-. 305 nmol/l, P < 0.05) and the calculated myocardial inosine release (-28 .+-. 32%) changed to extraction values (10 .+-. 17%, P < 0.0125). Coronary venous hypoxanthine during angina (990 .+-. 350 nmol/l) diminished (725 .+-. 230 nmol/l, P < 0.05) the arterial values (895 .+-. 320 nmol/l) decreased (795 .+-. 310 nmol/l, P = N.S.) and the myocardial hypoxanthine release (-15 .+-. 32%) with wide individual variability changed to mean extraction values (3.8 .+-. 26%, P = N.S.). The improved myocardial uptake of inosine and hypoxanthine after pindolol indicates that .beta.-blockade reduces the ATP catabolism. Despite the diminished mean myocardial lactate production after pindolol, ischemic myocardial energy deficiency may be less marked. The enhanced myocardial uptake of the ATP catabolites is derived from the beneficial effect of .beta.-blockade on myocardial O2 balance.