Regulation of primate angiotensin II receptors during altered sodium intake

In the rat, angiotensin II receptors of the adrenal glomerulosa and smooth muscle undergo reciprocal regulatory changes that parallel the changes in target cell sensitivity to angiotensin II during altered sodium intake. In primates, the relative importance of angiotensin II receptor regulation during sodium-induced changes in angiotensin II sensitivity is not clear. To evaluate the role of angiotensin II receptor regulation in the primate, we analyzed the changes in angiotensin II receptors of adrenal and bladder membrane-rich particles after 4 to 6 days of high or low sodium intake in the monkey (Macaca fascicularis). Consistent with the decreased pressor response to angiotensin II, smooth muscle angiotensin II receptors were fewer in sodium-restricted monkeys (93 +/- 17 fmol/mg) than in sodium-loaded monkeys (171 +/- 6 fmol/mg). However, in contrast to the rat, changes in zona glomerulosa angiotensin II receptors in monkey adrenal were similar to those in smooth muscle, decreasing with sodium restriction and increasing with sodium loading (344 +/- 64 and 660 +/- 68 fmol/mg, respectively). There was no change in angiotensin II receptor affinity in either smooth muscle or adrenal particles during altered sodium intake. Concomitant with the decrease in adrenal angiotensin II receptors, 18-hydroxylase activity was increased twofold in adrenal mitochondria from sodium-restricted monkeys (74 +/- 8 fmol/mg/min) compared with sodium-loaded animals (28 +/- 11 fmol/mg/min). The increased sensitivity of the primate adrenal to angiotensin II despite a fall in angiotensin II receptors indicates that full activation of steroidogenesis by angiotensin II can be maintained with partial receptor occupancy.(ABSTRACT TRUNCATED AT 250 WORDS)