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2251240 
Journal Article 
Effect of Nitroglycerin on Phosphorylase Activity of the Myocardium 
Markova, GA; Vyalykh, MF 
1974 
Yes 
Bulletin of Experimental Biology and Medicine
ISSN: 0007-4888
EISSN: 1573-8221 
NIOSH/00127253 
77 
4 
399-401 
The in-vitro and in-vivo effects of nitroglycerin (55630) on myocardial phosphorylase activity was investigated in rat hearts. Hearts were frozen, ground into powder, extracted with buffer, and incubated with 0.002 molar nitroglycerin. Rats were anesthetized intraperitoneally with 40 milligrams per kilogram (mg/kg) pentobarbital and then injected in the caudal vein with 1mg/kg nitroglycerin. The hearts were removed 1, 5, 10, and 20 minutes later to determine phosphorylase activity. Nitroglycerin had no effect on phosphorylase activity in heart muscle extract. The relative percentage of phosphorylase-a increased after in-vivo nitroglycerin injection, particularly after 5 and 10 minutes. A concomitant decrease in phosphorylase-b activity resulted in an overall decrease in phosphorylase. The authors conclude that the overall decrease in phosphorylase activity indicates that nitroglycerin exerts an effect on myocardial metabolism other than its adrenergic effect. A possible mechanism is the action of nitroglycerin on the phosphatase of phosphorylase. Fluctuations in phosphorylase-b and phosphorylase-a activity 5 to 10 minutes after nitroglycerin injection are attributed to phosphatase activity.