Hypoxia-induced release of atrial natriuretic factor (ANF) from the isolated rat and rabbit heart

The effect of hypoxia on the release of atrial natriuretic factor (ANF) was studied in isolated, constant-flow perfused hearts of rats and rabbits. Effluent samples were frozen pending extraction and radioimmunoassay of ANF. Hypoxia (10 min) caused a 3.9-fold (rats) and 4.6-fold (rabbits) increase of ANF release over control values. ANF release returned to control levels within 8-11 min of reoxygenation. Prolonged (20 min) hypoxia evoked further ANF release. The increase in ANF release and decrease in ventricular pressure, heart rate and coronary perfusion pressure were fully reversible, suggesting that tissues were not damaged. These results demonstrate that hypoxia induces a massive release of ANF by an as yet unexplained mechanism.