AJP - Heart and Circulatory Physiology, Vol 249, Issue 4 763-H769, Copyright © 1985 by American Physiological Society
Contraction regulates myosin synthesis and myosin content of cultured heart cells
P. McDermott, M. Daood and I. Klein
Cultured neonatal rat heart cells are a useful model for studying the
regulation of myocyte growth. The myosin content of heart cells increases
between days 1 and 4 in culture. To determine if contraction per se can
regulate myocyte growth, myosin content and protein synthesis were compared
in spontaneously contracting and noncontracting cultured heart cells.
Myosin content, assayed as the total myosin ATPase activity per culture
dish, was significantly increased in contracting cells after 3, 4, and 5
days in culture. Protein synthesis was measured by incorporation of
[14C]lysine into total cell protein and into sodium dodecyl
sulfate-polyacrylamide gel electrophoresis resolved myosin. Contraction
stimulated both total cell protein content and protein synthesis by day 3
in culture. Compared with heart cells arrested with 50 mM KCl, myosin
synthesis was significantly increased by 96, 112, and 46% at days 2, 3, and
4, respectively. Similar results were observed when myosin content and
protein synthesis in contracting myocytes were compared with cells arrested
with either 25 mM KCl or 10(-5) M verapamil. The present studies suggest
that contraction increases the myosin content in cultured heart cells and
that this increase is mediated via a stimulation of myosin synthesis in
association with cell growth.
