AJP - Endocrinology and Metabolism, Vol 259, Issue 3 E413-E421, Copyright © 1990 by American Physiological Society
Insulin stimulates mitochondrial protein synthesis and respiration in isolated perfused rat heart
E. E. McKee and B. L. Grier
Department of Biological Chemistry and Structure, University of Health Sciences, Chicago Medical School, Illinois 60064.
The rates of synthesis of mitochondrial proteins by both the cytoplasmic
and mitochondrial protein synthetic systems, as well as parameters of
respiration, were measured and compared in mitochondria isolated from
fresh, control perfused, and insulin-perfused rat hearts. The respiratory
control ratio (RCR) in mitochondria from fresh hearts was 8.1 +/- 0.4 and
decreased to 6.0 +/- 0.2 (P less than 0.001 vs. fresh) in mitochondria from
control perfused hearts and to 6.7 +/- 0.2 (P less than 0.005 vs. fresh and
P less than 0.02 vs. control perfused) for mitochondria from hearts
perfused in the presence of insulin. A positive correlation between the RCR
and the rate of mitochondrial translation was demonstrated in mitochondria
from fresh hearts. In mitochondria isolated from control perfused hearts,
the rate of protein synthesis decreased to 84 +/- 3% of the fresh rate
after 30 min of perfusion and fell further to 64 +/- 3% after 3 h of
perfusion. The inclusion of insulin in the perfusion buffer stimulated
mitochondrial protein synthesis 1.2-fold by 1 h (P less than 0.005) and
1.34-fold by 3 h of perfusion (P less than 0.001). The addition of insulin
to 1-h control perfused hearts shifted the rate of mitochondrial protein
synthesis from the control level to the insulin-perfused level within 30
min of additional perfusion, whereas 1 h was required to shift the RCR
values of these mitochondria from control levels to insulin-perfused
levels. Thus, whereas RCR was a useful predictor of mitochondrial
translation rates, it did not account for the effects of insulin on
mitochondrial translation.(ABSTRACT TRUNCATED AT 250 WORDS)
