AJP - Heart and Circulatory Physiology, Vol 253, Issue 5 1005-H1011, Copyright © 1987 by American Physiological Society
Changes in LV papillary muscle performance and myosin composition with aortic insufficiency in rats
C. S. Apstein, Y. Lecarpentier, J. J. Mercadier, J. L. Martin, F. Pontet, C. Wisnewsky, K. Schwartz and B. Swynghedauw
Institut National de la Sante et de la Recherche Medicale U127, Hopital Lariboisiere, Paris, France.
Aortic insufficiency was induced in rats. Left ventricular papillary muscle
function was studied after 5, 12, and 40 wk and compared with the papillary
muscles from sham-operated animals. The maximum unloaded velocity of
shortening, Vmax, was decreased in the rats with aortic insufficiency
relative to controls by 15, 20, and 34% at 5, 12, and 40 wk, respectively.
The decrease in Vmax occurred concomitantly with a change in the myosin
isoenzyme composition such that the V1 isoform content decreased and the V3
isoform increased. Relative to age-matched controls, the V3 content in the
hearts with aortic insufficiency had increased by 80, 180, and 125% at 5,
12, and 40 wk, respectively. The decrease in Vmax in the aortic
insufficiency group muscles correlated with the change in myosin isozyme
composition and could not be explained by changes in collagen content. Thus
aortic insufficiency induced changes in myosin isozyme content and Vmax
similar to those previously observed with aortic stenosis, thus suggesting
a common mechanism of myocardial adaptation to different types of
mechanical overload.
