Effects of dietary sodium on angiotensin II receptors from rabbit adrenal cortex and aorta.

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Abstract
Sodium intake reciprocally influences adrenal and vascular responses to angiotensin II. The modulating action of sodium could occur at the receptor level of these organs. In he present study, we characterized the angiotensin II receptors from the rabbit adrenal cortex and aorta at the subcellular level and examined the effects of sodium balance on these receptor sites. 125I-angiotensin II bindings to rabbit adrenal and aortic membrane fractions were demonstrated to have features consistent with those of biologically relevant receptors with high affinity, limited capacity and specificity for angiotensin II. The binding affinities and capacities of these adrenal and aortic receptors were compared between rabbits maintained on high and low sodium diets for 6 weeks. The binding capacity of adrenal receptors from low sodium intake animals, which had higher levels of plasma angiotensin II, was 45% significantly increased than that from high sodium intake animals, Affinity constants of adrenal receptors from high and low sodium intake groups were not significantly varied. On the other hand, either the affinity constant or the binding capacity of aortic receptors between these two groups was not significantly different. The variation of the binding capcity of adrenal receptors during alterations of sodium intake did not seem to be related to changes of other membrane constituents. These results suggest that during changes of sodium intake altered adrenal angiotensin II receptor content might be responsible for the control of adrenal sensitivity to angiotensin II, but the changes in vascular responsiveness to angiotensin II need not be accompanied by alterations of the aortic angiotensin II receptor itself.

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