Modulation of catecholamine effects during hypoglycaemia in man by urapidil and propranolol

The hypothesis that in hypoglycaemia adrenoceptor-blocking drugs may enhance those metabolic effects of the catecholamines that remain unblocked has been investigated in 12 volunteers. alpha-Adrenoceptor blockade with urapidil increased the heart rate and the plasma noradrenaline level, and increased the beta-adrenoceptor mediated cellular uptake of potassium and phosphate, and the production of lactate. Posthypoglycaemic glucose intolerance and the counterregulatory responses of hGH and cortisol remained unchanged. Plasma adrenaline, the alpha-adrenoceptor mediated responses of cortisol and hGH, and the diastolic blood pressure were increased by propranolol. Adrenoceptor blocking drugs produce an indirect stimulatory effect by eliciting a reflex increase in sympathetic tone, which is manifested as stimulation of receptors of the type that has not been blocked.