AJP - Endocrinology and Metabolism, Vol 247, Issue 6 781-E785, Copyright © 1984 by American Physiological Society
Protein turnover in heart and diaphragm of rat fetus
J. D. Johnson and D. L. Wetmore
Fractional rate constants for protein synthesis (KS) in fetal rat heart and
diaphragm were determined by the constant infusion technique. Uniformly
labeled [14C]tyrosine was infused at a constant rate into the maternal
jugular vein of unanesthetized unrestrained pregnant rats for 6-10 h at
days 19 and 21 of gestation and KS calculated from the protein-bound to
tissue-free tyrosine specific radioactivity ratio and the rate constant for
attainment of plateau tyrosine specific radioactivity in fetal plasma
(lambda p). Rate constants for protein degradation (KD) were calculated by
subtracting fractional growth rate (KG) from KS. In both tissues, protein
accretion during the most rapid phase of growth (day 19) was accomplished
by greater rates of synthesis and lower rates of degradation when compared
with a time of lesser growth (day 21).
