AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 1 33-R39, Copyright © 1995 by American Physiological Society
Interaction of hypertension and caloric restriction on cardiac mass and isomyosin expression
S. J. Swoap, P. Boddell and K. M. Baldwin
Department of Physiology and Biophysics, University of California, Irvine 92717.
Previous studies show that elevations in blood pressure induce concomitant
increases in both cardiac mass and slow beta-myosin heavy chain (MHC)
expression in rodents, whereas caloric restriction of 50% (CR) causes an
increase in beta-MHC while modestly lowering blood pressure in normotensive
rats. The goals of this study were to 1) determine if beta-MHC expression
could be independently regulated by CR and hypertension when these two
interventions are combined and 2) determine if CR exerts a lowering of
blood pressure in two contrasting models of rodent hypertension. Rodents
were assigned to the following groups: 1) normal control (NC); 2) abdominal
aortic constriction (Abcon), a model that induces hypertension via
renin-angiotensin II; 3) nephrectomy-deoxycorticosterone acetate treatment
(DOCA), a model that induces hypertension through increased salt retention;
4) CR; 5) Abcon+CR; 6) DOCA+CR. Results show that both Abcon and DOCA
induced significant increases in systemic blood pressures, left ventricular
(LV) weight/body weight, and the relative content of beta-MHC compared with
NC. When applied in combination with either Abcon or DOCA, CR significantly
blunted the changes observed in both systemic blood pressures and LV
weight/body weight. In contrast, CR in conjunction with DOCA augmented %
beta-MHC expression relative to either DOCA or CR alone. These data suggest
1) caloric restriction exerts a powerful impact on reducing experimentally
induced hypertension in rodents and 2) the regulation of beta-MHC
expression appears to be regulated by at least two processes, one
associated with the stimulus of hypertension and the other involving an
independent pathway linked to caloric restriction.
