INFLUENCE OF O-2 DEPRIVATION, REDUCED FLOW, AND TEMPERATURE ON RELEASE OF ANP FROM RABBIT HEARTS

The separate effects of hypoxia and ischemia on atrial natriuretic pep tide (ANP) release were evaluated in Langendorff-perfused rabbit heart s. Heart rate, coronary flow, and atrial and ventricular volumes were kept constant. Hypoxia was induced for 20 min at room temperature in s even hearts and at 37 degrees C in a second group of seven hearts. A t hird group of eight hearts was subjected to global ischemia for 20 min by reducing coronary flow to 1 ml/min at room temperature. All hearts were reoxygenated/reperfused at 37 degrees C for 30 min. Hypoxia at 3 7 degrees C induced a significant increase in ANP release. In contrast , both room temperature hypoxia and ischemia were characterized by a s ignificant decrease in ANP release, despite hemodynamic alterations si milar to those recorded during hypoxia at 37 degrees C. Both reoxygena tion and reperfusion induced a prompt reversal of the changes of ANP r elease observed during the period of oxygen deprivation. These data de monstrate that decreased oxygen availability and reduced coronary flow are not the primary factors affecting release of ANP during ischemia and that alterations of myocardial temperature may play a major role i n this phenomenon.