On the mechanism of renin release during experimental myocardial ischaemia.

An increase in plasma renin activity (PRA) following experimental coronary occlusion has previously been demonstrated in anaesthetized and conscious dogs. The purpose of the present study was to analyse the mechanism of this renin release. In two distinct models of myocardial ischaemia in anaesthetized dogs--i.e. occlusion of the left-anterior descending coronary artery (model A, n = 21) and atrial pacing in the presence of stenosis of the left-anterior descending coronary artery (model B, n = 23), an increase in arterial PRA was found from 1.68 +/- 0.43 to 3.06 +/- 0.63 ng ml-1 h-1 (model A, mean +/- SEM, P less than 0.025) and from 9.87 +/- 3.59 to 14.96 +/- 4.06 ng ml-1 h-1 (model B, P less than 0.05), respectively. The increase in PRA following coronary occlusion was not blunted by adrenergic beta-receptor blockade with propranolol (3 mg kg-1 i.v.; n = 4). Coronary sinus PRA was lower than arterial PRA and the increase in PRA did not occur in nephrectomized dogs (n = 5). The data suggest that myocardial ischaemia induces a release of renin from the kidney which is not mediated by adrenergic beta receptors.