[Effect of pretreatment with atenolol and propranolol on sympatho-adrenal and cardiovascular responses to acute insulin-induced hypoglycaemia in the hypertensive patient].

Plasma catecholamines and cardiovascular responses to acute insulin i.v. injection (0.12 U.I. per Kg of body weight) have been studied in eight patients with mild essential hypertension. The hypoglycaemia test was carried out before and after a week of atenolol treatment. In six patients the test was also repeated after propranolol treatment. Following insulin injection, blood sugar fell abruptly with a nadir at 30 m, diastolic blood pressure decreased, and systolic blood pressure and heart rate rose significantly. Atenolol treatment abolished almost completely these hemodynamic changes. By contrast, propranolol caused an increase in both systolic and diastolic blood pressures, leaving the heart rate unmodified. During hypoglycaemia, plasma adrenaline rose sharply in coincidence with the glycaemic nadir and declined thereafter during the glycaemic recovery. Plasma noradrenaline rose less markedly than adrenaline, but the increments were significant after 30 and 60 m. Neither atenolol, nor propranolol affected significantly these changes in plasma catecholamine concentration. These data indicate that beta-blockers do not alter the hypoglycaemia-induced adrenomedullary release of catecholamines. We conclude therefore that beta-blockers modify the pattern of the hemodynamic response to acute hypoglycaemia by interfering with the peripheral effects of circulating catecholamines in a way which depends on the degree of beta-1 selectivity of the drug used.