Hypertension, Vol 13, 77-82, Copyright © 1989 by American Heart Association
DJ DiPette, PE Greilich, NE Kerr, GA Graham and OB Holland
This study was undertaken to determine the systemic and regional
hemodynamic effects of long-term dietary calcium supplementation in
mineralocorticoid (DOC)-salt hypertension. Systemic and regional
hemodynamic measurements were determined by the radioactive microsphere
technique in conscious and unrestrained rats (kidneys intact) with DOC-
salt-induced hypertension that were pair-fed either a normal calcium (0.6%
by weight, n = 12) or a calcium-supplemented (high-calcium) diet (2.5% by
weight, n = 12). After 7 to 8 weeks, there were no differences in weight,
heart rate, or cardiac output between the two groups. In contrast, the
high-calcium rats had a significantly lower mean blood pressure (125 +/- 4
mm Hg, mean +/- SEM) than the normal calcium rats (143 +/- 5 mm Hg); this
finding appeared to result predominantly from a reduction in total
peripheral resistance. The high-calcium rats had a higher renal blood flow
(7.8 +/- 0.5% vs. 6.2 +/- 0.4% cardiac output; p less than 0.05) and lower
renal (14.3 +/- 1 vs. 19.3 +/- 2 mm Hg/min/ml/g tissue; p less than 0.05)
and jejunal vascular resistance than did the normal calcium rats. Two
additional identical groups of normal calcium-and high-calcium-DOC-salt
rats (n = 12 each) were also studied. In these rats, serum-ionized calcium
decreased significantly (p less than 0.05) from baseline in both groups.
Urinary sodium increased in both groups but did not differ significantly.
In conclusion, dietary calcium supplementation attenuates the rise in
peripheral vascular resistance that accompanies DOC-salt hypertension. This
attenuated resistance appears to be relatively selective and is noted
particularly in the renal vasculature.
ARTICLES
Systemic and regional hemodynamic effects of dietary calcium supplementation in mineralocorticoid hypertension
Department of Internal Medicine, University of Texas Medical Branch, Galveston 77550.
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