AJP - Renal Physiology, Vol 260, Issue 5 657-F662, Copyright © 1991 by American Physiological Society
Dietary calcium modulates renal BBM angiotensin II binding and Na(+)-H+ antiporter activity in SHR
M. Levi and W. L. Henrich
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas.
Dietary Ca is an important modulator of blood pressure in the spontaneously
hypertensive rat (SHR). Since the kidney plays a key role in the
pathogenesis of hypertension, the purpose of this study was to determine
the potential renal mechanisms of the blood pressure-lowering effect of
increasing dietary Ca content. In 21-day-old SHR fed 0.1 vs. 3.6% Ca diet
for 14 days, increasing dietary Ca had no significant effects on basal [704
+/- 50 in 0.1% Ca vs. 784 +/- 61 ng angiotensin I (ANG I).mg-1.h-1 in 3.6%
Ca, P = not significant (NS)], isoproterenol-stimulated (1,057 +/- 52 in
0.1% Ca vs. 1,104 +/- 59 ng ANG I.mg-1.h-1 in 3.6% Ca, P = NS), or
angiotensin II (ANG II)-inhibited (370 +/- 50 in 0.1% Ca vs. 411 +/- 39 ng
ANG I.mg-1.h-1 in 3.6% Ca, P = NS) renal superficial cortical slice renin
release. In contrast, in apical brush-border membrane (BBM) vesicles
isolated from the superficial cortex, increasing dietary Ca caused a
significant decrease in ANG II binding, which was mediated by a decrease in
the number of binding sites (Bmax, 376 +/- 14 in 0.1% Ca vs. 234 +/- 6 fmol
ANG II/mg BBM protein in 3.6% Ca, P less than 0.01), and no change in the
affinity [dissociation constant (Kd), 17.8 +/- 1.4 in 0.1% Ca vs. 13.4 +/-
2.8 nM ANG II in 3.6% Ca, P = NS].(ABSTRACT TRUNCATED AT 250 WORDS)
