AJP - Regulatory, Integrative and Comparative Physiology, Vol 261, Issue 4 945-R949, Copyright © 1991 by American Physiological Society
The interactive effects of dietary sodium chloride and calcium on cardiovascular stress responses
K. E. Scrogin, D. C. Hatton and D. A. McCarron
Department of Medical Psychology, Oregon Health Sciences University, Portland 97201-3098.
Blood pressure increases associated with salt loading in the spontaneously
hypertensive rat (SHR) are attenuated with increased dietary calcium. To
assess the cardiovascular effects of these nutrients during stress, blood
pressure and sympathoadrenal responses to stress were compared in
salt-sensitive SHRs fed diets containing normal (0.73%) or high (8.0%) NaCl
combined with either low (0.2%) or high (2.0%) calcium. NaCl-loaded rats
showed increased blood pressure and exaggerated plasma epinephrine changes
during restraint stress. Elevated blood pressure responses to exogenous NE
were also observed with high salt intake. Supplementary calcium reduced
blood pressure and attenuated the hypertensive effect of NaCl during
restraint stress. Animals fed the high calcium diets had lower plasma
epinephrine levels while vascular reactivity was not affected. The results
indicate that increased sympathoadrenal activity and vascular reactivity
contribute to elevated blood pressure and exaggerated pressor responses
produced by NaCl loading in the salt-sensitive SHR. However, the
hypotensive effects of dietary calcium appear to be related to
sympathoadrenal activity but not vascular reactivity.
