Effect of exogenous insulin on blood pressure regulation in healthy and diabetic subjects.

To define the role of insulin in blood pressure regulation, the hormone's action on renal sodium handling, potassium balance, pressor reactivity, and the release of catecholamines and aldosterone are summarized. Insulin-stimulated renal sodium reabsorption induces expansion of the extracellular volume, increase in cardiac output, and ultimately, hypertension. On the other hand, the insulin-induced shift of potassium into the cell interior is transient and appears to be of little consequence for long-term blood pressure control. Although the release of norepinephrine is stimulated by insulin, a norepinephrine-mediated pressor effect is prevented in healthy men by a simultaneous norepinephrine-antagonistic action of insulin. The latter causes the fall in blood pressure seen after intravenous insulin in patients with autonomic dysfunction who lack the rise in norepinephrine release. Both in healthy and in diabetic men, exogenous insulin does not modify the pressor effect of angiotensin II, although it impairs the secretion of aldosterone during stimulation by supraphysiological doses of angiotensin II.