P K Das

University of Manitoba, Winnipeg, Manitoba, Canada

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Publications (5)14.81 Total impact

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    ABSTRACT: The effects of propranolol (1–5 mg/kg) on the ultrastructure and high energy phosphate content of dog myocardium were investigated after 2 h of ischemia and 2 h of reperfusion. Two adjoining major ventricular branches of the left circumflex coronary artery were occluded to produce ischemia. Propranolol was administered intravenously just before occlusion of the coronary arteries in all the experiments. Two hours of ischemia caused structural changes and significantly reduced creatine phosphate (CrP) and ATP contents, and increased AMP levels. Propranolol (5 mg/kg) had no effect on these ischemic changes.Propranolol was found to protect the myocardium from structural damage usually observed after 2 h of reperfusion. The size and number of amorphous electron-dense mitochondrial granules, which are considered to contain calcium, observed after reperfusion, were reduced in propranolol-treated animals. Stores of ATP and total nucleotides (ATP + ADP + AMP), and the ATP:AMP ratio were significantly higher in propranolol (5 mg/kg) treated dogs in comparison with the untreated controls after 2 h of reperfusion. There was, however, no difference between the CrP levels of propranolol-treated and untreated preparations. The study shows that propranolol is effective in reducing the reperfusion-dependent changes in ischemic myocardium. Reduction in the intracellular calcium overload as well as maintenance of the structural integrity of the cell, particularly that of mitochondria, may be involved in these protective effects of propranolol.
    Canadian Journal of Physiology and Pharmacology 10/1979; 57(9):979-86. DOI:10.1139/y79-147 · 1.77 Impact Factor
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    ABSTRACT: Changes in the intramuscular pH oscillations were examined by the use of an antimony electrode upon perfusing the isolated rat heart under different experimental conditions. The pH oscillations were decreased upon perfusing the hearts with Na+- or Ca2+-free medium and increased upon perfusing with K+-free medium. Increasing the temperature of perfusion medium from 25 to 40 degrees C or omitting glucose from the perfusing medium decreased the magnitude of oscillations. On the other hand, complete interruption of the perfusion flow resulted in an increase in the amplitude of pH oscillation. An initial increase followed by a decrease in the pH oscillation was seen when hearts were perfused with medium containing lactic acid at pH 6.6. These results suggest that pH oscillations reflect fluctuations in myocardial metabolism.
    Canadian Journal of Physiology and Pharmacology 09/1979; 57(8):900-7. DOI:10.1139/y79-137 · 1.77 Impact Factor
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    ABSTRACT: The effects of 30-, 60-, and 90-min occlusion of the left anterior descending coronary artery and 60-min reperfusion were studied on the left ventricular dP/dt, myocardial ultrastructure, and tissue as well as blood lactate levels in dogs. The dP/dt was depressed by the occlusion, and reperfusion instituted after 30 min resulted in full recovery whereas that after 90 min had an adverse effect. Varying degrees of ultrastructural damage were noted after 60 and 90 min of occlusion and this was further exaggerated by reperfusion. Coronary occlusion markedly increased lactate content of ischemic myocardium, and the same returned to normal upon reperfusion. Myocardial ischemia for 30 or 60 min did not affect net arterial lactate extraction by the heart, but ischemia for 90 min reversed net lactate extraction to net lactate production by the heart. Reperfusion after 30 min of occlusion significantly increased lactate extraction, but reperfusion after 60 and 90 min of ischemia significantly decreased net lactate extraction and increased net production, respectively. The results indicate that estimation of net lactate exchange across the heart can be of value in assessing the viability of myocardium following coronary bypass surgery.
    Canadian Journal of Physiology and Pharmacology 01/1979; 56(6):1059-63. DOI:10.1139/y78-171 · 1.77 Impact Factor
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    W Chernecki · P.K. DAS · N.S. DHALLA · G.P. SHARMA
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    ABSTRACT: 1 The effects of 5 mg/kg acebutolol given intravenously were investigated in anaesthetized dogs after (a) ligation of the left anterior descending coronary artery and (b) coronary reperfusion following 60 min of ligation of the anterior descending coronary artery. 2 Coronary artery ligation produced, after 4 to 6 h, persistent multiple ventricular ectopic beats and abnormalities of R and T waves and of the S-T segment. Administration of acebutolol, after the development of persistent ventricular arrhythmias, restored normal sinus rhythm within 5 min of injection. Electrocardiographic abnormalities were also reduced. 3 Coronary artery reperfusion (following 60 min of ligation) resulted in multiple ventricular ectopic beats, ventricular tachycardia and/or ventricular fibrillation. Pretreatment with acebutolol, 15 min before starting reperfusion, markedly reduced the arrhythmias. 4 Acebutolol did not affect peak inspiratory airway pressure. 5 Acebutolol produced significant bradycardia and slight, transient, hypotension. It was without effect on left ventricular systolic pressure, left ventricular end-diastolic pressure, cardiac output or pulmonary arterial pressure. 6 These results suggest beneficial effects of acebutolol in myocardial ischaemia and coronary reperfusion, without any significant risk of cardiodepression or bronchospasm.
    British Journal of Pharmacology 11/1978; 64(2):265-72. DOI:10.1111/j.1476-5381.1978.tb17299.x · 4.84 Impact Factor
  • N S Dhalla · P K Das · G P Sharma
    Journal of Molecular and Cellular Cardiology 05/1978; 10(4):363-85. DOI:10.1016/0022-2828(78)90384-X · 4.66 Impact Factor