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Regional myosin heavy chain isoform expression in response to exercise training in old rat myocardium
Author(s) -
Chung Eunhee,
Dorton Benjamin J.,
Diffee Gary M.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1447
Subject(s) - myosin , major histocompatibility complex , gene isoform , ventricle , medicine , apex (geometry) , endocrinology , mhc class i , biology , chemistry , anatomy , immunology , immune system , biochemistry , gene
It is recognized that with ageing of the rodent heart there is a shift in myosin heavy chain (MHC) isoform from α‐MHC to β‐MHC. Previous studies have shown evidence of significant regional differences in MHC expression across the wall of the myocardium in young adult rats, but little is known regarding regional variations in MHC isoforms with age or with adaptation to exercise training in old rats. The objective of this study was to determine the regional variations of MHC expression in response to exercise training in 30 mo male Fischer 344/BNF 1 rats. Rats were divided into trained (T) and control (C) groups. T rats underwent 11 weeks of treadmill exercise training in which the intensity and duration were progressively increased until week 7 when rats were running at 13 m/min, 10% grade for 35 min. At the end of training period (at 33 mo), hearts were excised and weighed. The left ventricle was divided into apex and mid‐myocardium and the mid‐myocardium further divided into endocardial (ENDO) and epicardial (EPI) regions. There were no significant differences in ventricular weight (VW) and VW/tibia length between T and C. The MHC isoform content of ventricular homogenates was determined using a 6 % SDS‐PAGE. The α‐MHC content (as a percent of total MHC) was 42 ± 6 % in Apex, 40 ± 7% in EPI, and 35 ± 7% in ENDO. The difference in α‐MHC content between the Apex and ENDO regions was significant (p =0.02). However, there was no significant effect of training on α‐MHC content. We concluded that the age‐related decrease in α‐MHC is regionally variable and is not reversible in response to exercise training in aged FBNF1 rats.