J. Biol. Chem., Vol. 255, Issue 23, 11149-11155, Dec, 1980
The regulation of protein turnover in newborn rat heart cell cultures
C Frelin
The regulation of myocardial protein turnover was studied using newborn rat
heart cells in monolayer cultures. Protein accumulation in this model
system was regulated by the presence of serum in the culture medium. The
influences of serum on the rates of protein synthesis and degradation were
investigated. Serum deprivation or arginine deprivation did not modify
protein synthesis. In contrast serum strongly inhibited the rates of
[3H]leucine release from prelabeled long-lived myocardial proteins. The
inhibiting serum factor was found heat-stable, displayed slight species
specificity, was of plasmatic origin, and its activity was decreased in the
plasma of hypophysectomized rats. Platelet growth factor, which promotes
DNA synthesis in heart cell cultures, did not inhibit protein degradation.
The influence of known regulators of myocardial protein balance was
investigated. Leucine had no influence on protein synthesis and
degradation. Supraphysiological concentrations of insulin and growth
hormone inhibited protein degradation but only in the absence of serum. It
is suggested that these compounds may not be the natural regulators of
myocardial protein balance.
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