Dietary calcium modulates renal BBM angiotensin II binding and Na(+)-H+ antiporter activity in SHR.
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)
Levi
M
M
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas.
Henrich
W L
WL
D000804:Angiotensin II / Q000378:metabolism*; D000818:Animals; D002136:Calcium, Dietary / Q000494:pharmacology*; D002352:Carrier Proteins / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D008871:Microvilli / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR / Q000378:metabolism*; D012083:Renin / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers
D002136:Calcium, Dietary; D002352:Carrier Proteins; D017923:Sodium-Hydrogen Exchangers; D000804:Angiotensin II; D012083:Renin