AJP - Endocrinology and Metabolism, Vol 245, Issue 5 508-E514, Copyright © 1983 by American Physiological Society
Regulation of protein synthesis in lung by amino acids and insulin
J. M. Besterman, C. A. Watkins and D. E. Rannels
Acute effects of amino acid availability and insulin on protein synthesis
were investigated in rat lungs perfused in situ with buffer containing
either 4.5% fraction V bovine serum albumin (FrV BSA), 4.5% essentially
fatty acid-free (FAF) BSA, or 4.5% dextran to maintain colloid osmotic
pressure. In the presence of FrV BSA, protein synthesis was unaffected by
perfusion for 1 or 3 h with buffer containing no added amino acids (0X), as
compared with amino acids at concentrations one (1X) or five (5X) times
those in rat plasma. Regardless of the amino acid concentration, addition
of insulin was without effect. Likewise, in lungs perfused for 1 h with
either FAF BSA or dextran, protein synthesis was insensitive to amino acid
availability or to insulin. After 3 h, however, protein synthesis decreased
34 and 37%, respectively, when these lungs were perfused in the absence of
both amino acids and insulin. In both cases, the inhibition was prevented
by addition of insulin to the perfusate; addition of the hormone to
perfusate containing 1X amino acids or elevating perfusate amino acids to
5X did not affect protein synthesis. The deficit in protein synthesis
observed in the absence of both amino acids and insulin was not accompanied
by ATP depletion or by lower intracellular concentrations of amino acids.
Similarly, the effect of insulin was not associated with a general
elevation in intracellular amino acid concentrations.(ABSTRACT TRUNCATED AT
250 WORDS)
