The influence of captopril on the epinephrine response to insulin-induced hypoglycemia in humans. The interaction between the renin-angiotensin system and the sympathetic nervous system

The aim of this study was to assess whether an interaction exists between the renin-angiotensin system and the sympathetic nervous system at the level of the adrenal medulla during insulin-induced hypoglycemia in normal humans. Seventeen healthy volunteers were studied in a randomized, single-dose, double-blind, cross-over fashion using 25 mg captopril v placebo followed by an intravenous injection of 0.15 IU/kg insulin. Blood samples were obtained before and at 15 min intervals after insulin injection. Both plasma glucose level and heart rate were identical during captopril and placebo at rest and after insulin. Plasma renin activity increased after insulin and captopril. The increase in plasma epinephrine was lower after insulin and captopril compared to after insulin and placebo. Likewise the increase in plasma norepinephrine was blunted on insulin and captopril. Thus, when the generation of angiotensin II was blocked by captopril the insulin-induced rise in epinephrine and norepinephrine was blunted. This indicates that an interaction exists between the renin-angiotensin system and the sympathoadrenal system.