Increased coronary venous inorganic phosphate concentrations during experimental myocardial ischemia

Abstract

The concentration of inorganic phosphate in coronary venous blood draining the ischemic myocardium is increased. After coronary arterial ligation (46 dogs, thoracotomy), the mean increase in local venous inorganic phosphate concentration was about 75 percent of the basal value; peak concentrations were reached 5 to 15 minutes after arterial ligation. The increased venous phosphate concentration was considered to be derived from the ischemic tissue because (1) myocardial biopsy specimens showed an increased content of inorganic phosphate, whereas the tissue high-energy phosphate compound contents were decreased; (2) venous blood leaving nonischemic tissue did not have an increased concentration of phosphate; and (3) inorganic phosphate was released by Ischemic rat hearts perfused in the absence of red blood cells. Coronary sinus inorganic phosphate concentrations were increased when more than 15 percent of the volume of the heart was ischemic. Comparing increases in coronary venous inorganic phosphate during ischemia with increases of lactate and potassium, venous lactate and phosphate both increased 15 to 20 percent above the arterial level but potassium only increased 5 percent. Venous inorganic phosphate changes specifically reflect the intracellular breakdown of high-energy phosphate compounds.