Sodium intake and vascular smooth muscle responsiveness to norepinephrine and angiotensin in the rabbit.

The effect of dietary sodium restriction on the responses to norepinephrine and angiotensin was assessed in two vascular smooth muscle preparations in the rabbit. Sodium restriction reduced the response to angiotensin of both the limb vessels in vivo and the aorta in vitro. The response to norepinephrine was potentiated by sodium restriction in both preparations. The effects on angiotensin responsiveness did not appear to be related to tachyphylaxis, changes in extracellular electrolyte composition, or nonspecific depression of smooth muscle function. Probably, the change in sodium intake induced a change in the smooth muscle cell membranes which modified the affinity of their receptors for angiotensin and norepinephrine.