Studies of Coronary Disease in the Experimental Animal. Ii. Polarographic Determinations of Local Oxygen Availability in the Dog's Left Ventricle During Coronary Occlusion and Pure Oxygen Breathing 1

Abstract

In experiments previously reported (1) it was found that platinum electrodes for polarographic measurement of oxygen availability have given fairly steady control readings in the left ventricular muscle of the dog. When the animals breathed pure oxygen, electrode readings rose 50-200%o. When a coronary branch was occluded they declined considerably at the borders of the ischemic area, approached zero at its center, and returned to the base line shortly after release of the ligature. If the artery was occluded with the dog breathing room air, pure oxygen breathing did not change values at the center of the ischemic area. However, it did cause a rise in the readings at the "borders" before the occlusion was released. These conclusions were based on studies of 12 anesthetized dogs using two or three electrodes simultaneously in each experiment.We have since developed a more stable dog preparation, using larger numbers of electrodes and obtaining more frequent readings which give a more complete description of the changes in local oxygen availability during short periods of coronary occlusion. Our particular concern has been to learn the size of the "border" areas that may be favorably affected by oxygen inhalation as well as the magnitude and regularity of the oxygen effect. This paper will describe the method we now use, and present a statistical analysis of the results of the first seven experiments in which we have used it. These studies would seem to have a bearing on the 1 This investigation was supported by research grants from the National Heart Institute, of the National Institutes of Health, Public Health Service (USPH-398 and 392) and from the Life Insurance Fund for Medical Research.use of oxygen inhalation for the treatment of acute myocardial infarction in man. METHODApparatus. In our earliest experiments we used the polarographic apparatus described by Montgomery and Horwitz (2) for use in the skin. Since then certain modifications have been made. We now use continuous electrolysis with six to 10 electrodes in the circuit at all times, their individual current variations being recorded when desired on a D'Arsonval galvanometer with a sensitivity of 5 X 10' amps./mm. The circuit modification is shown in Figure 1 and described in its legend. Open tip platinum electrode construction and the principles of polarography as applied to animal tissues have been described by Davies and Brink (3) and Montgomery and Horwitz (4). For the indifferent electrode we have found it necessary to immerse the dog's entire hind foot in a glass dish of saturated NaCl solution from which contact is made to the salt bridge of a calomel half cell. For electrode connections to the switch box No. 30 plain enameled wire was further insulated by placing it inside vinyl tubing. Anesthesia and gas administration. Healthy dogs weighing [15][16][17][18][19][20][21][22] Kgms. were given morphine sulfate intramuscularly (3 mg./Kgm.) followed in 45 minutes by slow intravenous injection of 0.25 cc./Kgm. of a mixture containing equal parts...

Effect of Glucose in Isoproterenol-Induced Necrotic Heart Under Anoxic Perfusion1

“…When the oxygenation of myocardial cell is compromised, the formation of ATP by oxidative phosphorylation is inhibited and the anaerobic glycolytic pathway be comes the major source of metabolic energy (1). It was reported that myocardial con tractility was only briefly maintained during a period of relative oxygen deprivation and the abrupt onset of myocardial anoxia caused a loss of contractility within a few beats (12). It was shown from the present study that, despite increased glycolysis, high energy phosphates and mechanical functions declined during 10 min of anoxia.…”

Polarographic Oxygen, the Epicardial Electrocardiogram and Muscle Contraction in Experimental Acute Regional Ischemia of the Left Ventricle

“…by an experimental teehnic previously described. 1 Under morphinepentobarbital-dial-urethane anesthesia, 1 the heart wns exposed, a coronary branch isolated, and an array of oxygen electrodes inserted, so as to sample muscle within and, insofar as possible, beyond the vessel's apparent left ventricular distribution. We utilized medium-sized or small arterial branches, which in these experiments were always derivatives of the left anterior descending.…”

“…This method avoided the undesirable effects of traction on a coronary ligature which were suspected of interfering with the stability of electrode reading in our previous work. 1 Slight increases of heart rate and blood pressure often resulted from dissection of the coronarj' artery or from placement of the forceps. Because of this, several minutes were allowed to elapse before initiation of any experimental procedure.…”

“…N PREVIOUS studies 1 ' 2 it has been shown that measurements of oxygen availability by the platinum electrode provide stable values in nonischemic myocardium as well as sensitive indices of ischemia produced by coronary occlusion. The borders of ischemic areas responded to oxygen inhalation by significant rises of myocardial oxygen, whereas the centers failed to show such a response.…”

Electrocardiogram, Myocardial Oxygen and Contraction in Scar and Collaterally Supplied Muscle After Experimental Coronary Ligation

“…morphine and dial-urethane-nembutal anesthesia, 2 and a smnll or medium-sized branch of the left anterior descending coronary artery was dissected free. An array of 8 to 10 light, glass-insulated platinum electrodes wns inserted.…”