Effects of oral calcium and potassium on endothelium-dependent relaxation in hypertensive rats.
High oral potassium (K) decreases stroke incidence in aging high salt-fed stroke-prone spontaneously hypertensive rats (SHRSP). We have seen high oral Ca increase stroke incidence in aging high salt-fed SHRSP without increasing blood pressure (BP) but with signs of K wasting. Therefore, we sought to determine whether high oral Ca suppresses the previously reported oral K-related enhancement of arterial endothelium-dependent relaxation as seen in younger high salt-fed SHRSP before the appearance of strokes. Four groups of female SHRSP were fed high-salt diets containing either low (0.4%) or high (1.6%) K with low (0.4%) and high (1.6%) Ca from age 1 to 4 mos. High oral K decreased BP independent of Ca intake (P < 0.05). High oral Ca did not affect BP. In contrast to aging SHRSP, high oral Ca neither increased urinary excretion nor decreased plasma concentration of K in these young adult SHRSP. However, high (vs. low) oral K only significantly reduced the half-maximal effective dose for acetylcholine-induced relaxation of aortic rings from rats fed low (18 +/- 3 vs. 38 +/- 6 nM, P < 0.05) not high Ca (25 +/- 5 vs. 31 +/- 3 nM). Neither oral K nor Ca affected nitroprusside-induced relaxation. Thus high oral Ca by itself does not impair endothelium-dependent relaxation in young adult high salt-fed SHRSP, but yet it suppresses the enhancing effect of high oral K on such relaxation and does so without altering BP, K balance, or endothelium-independent relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)
Peuler
J D
JD
Department of Internal Medicine, Wayne State University, Detroit, Michigan 48201.
Johnson
B A
BA
Schiebinger
R J
RJ
Zemel
M B
MB
Iannucci
A R
AR
D000109:Acetylcholine / Q000494:pharmacology; D000284:Administration, Oral; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000503:physiopathology*; D005260:Female; D006973:Hypertension / Q000503:physiopathology*; D009599:Nitroprusside / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D011918:Rats, Inbred SHR; D014664:Vasodilation / Q000187:drug effects*
D009599:Nitroprusside; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium