Molecular Pharmacology, Vol 14, 1167-1175, Copyright © 1978 by the American Society for Pharmacology and Experimental Therapeutics

A Selective Decrease of Collagen Peptide Synthesis by Dermal Polysomes Isolated from Glucocorticoid-Treated Newborn Rats

¹ Department of Biochemistry, School of Medicine, University of Vermont, Burlington, Vermont 05401

Polysomes were isolated from the dermis of control newborn rats treated with various pharmacological doses of triamcinolone diacetate and allowed to incorporate radioactive proline into collagen and noncollagen protein in the wheat germ lysate system. Proline incorporation into collagen and noncollagen protein was linearly related to the A₂₆₀ unit of polysomes added to the lysate system. Proline incorporation into collagen and noncollagen was maximal at 4.6 mM magnesium acetate, 155 mM potassium chloride, 0.017 mM amino acids and 40 µg protein of the wheat germ extract. Proline incorporation into collagen and noncollagen protein was dependent on the presence of amino acids, polysomes, adenosine triphosphate, potassium chloride, magnesium and wheat germ extract. Polysomes isolated form glucocorticoid-treated rats incorporated less proline into collagen as compared to proline incorporation into noncollagen protein, indicating a selective decrease of collagen synthesis, although proline incorporation into noncollagen protein was also decreased. This selective decrease of collagen synthesis was dose dependent. Significant inhibition of collagen synthesis was observed at a dose of 2 mg/kg. Maximum inhibition of collagen synthesis was observed at a dose of 12 mg/kg. This selective decrease in collagen synthesis was also dependent on the number of daily injections of glucocorticoid. A selective decrease of collagen synthesis was observed six hours after a single intraperitoneal injection of 12 mg/kg triamcinolone diacetate. After three daily injections of drug at this dose (12 mg/kg), the inhibitory effect on noncollagen and collagen syntheses was doubled. Since amino acids are not rate limiting in this protein synthesizing system in vitro, the glucocorticoid-mediated selective decrease of collagen synthesis in skin does not result from an inhibition of amino acid uptake.

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ACKNOWLEDGMENTS The authors wish to thank Paul Fives-Taylor for growing the E. coli cells for preparation of the tryptophan-labeled substrate.