Immunolocalization of rat cardiac [beta] myosin heavy chain protein
expression in systemic hypertension and caloric restriction.
Swoap, Steven J., Chris Gastellum, Paul Bodell, and Kenneth M.
Baldwin.
Department of Physiology and Biophysics, University of California,
Irvine, Irvine, CA 92717
APStracts 2:0167C, 1995.
Previous studies have shown that both systemic hypertension induced by
abdominal aortic constriction (Abcon) and 50% caloric restriction
(CR) increase left ventricular (LV) [beta] myosin heavy chain (MHC)
protein expression in the rat. However, these two physiological
states have different effects on hemodynamic load, and information
regarding [beta] MHC localization across the LV wall in these two
models may provide insight into the process of adaptation to chronic
stress among myocardial cells. Thus, the goal of this study was to
determine the pattern of [beta] MHC protein expression across the LV
wall in Abcon and CR using a [beta] MHC specific antibody. Adult
female Sprague-Dawley rats (approximately 225-250 g) were randomly
assigned to one of three groups: 1) normal control (NC); 2) Abcon;
and 3) CR. After a treatment period of 5 weeks, Abcon LVs
hypertrophied 52% relative to NC, accompanying the 42% increase in
mean blood pressure. CR, however, had a normal LV weight / body
weight ratio. The relative content of LV [beta] MHC protein
expression, as assessed by native gel electrophoresis, increased from
3% in NC to 25% and 41% in Abcon and CR, respectively.
Immunohistochemical analysis of [beta] MHC expression demonstrated
that the increase in [beta] MHC protein in the Abcon group occurred
primarily on the endocardial side of the LV. In contrast, the
increase in [beta] MHC protein in the CR LV occurred equally across
the entire LV wall. This suggests that caloric restriction has a
global effect on MHC isoform expression in LV myocardial cells. Thus,
the models of Abcon and CR affected different populations of
myocardial cells, consistent with previous findings suggesting that
these models upregulate [beta] MHC expression via different pathways.
Received 29 August 1994; accepted in final form 7 April 1995.
APS Manuscript Number C526-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 April 1995.