Glucocorticoid-mediated selective reduction of functioning collagen messenger ribonucleic acid

Abstract

Polysomes were isolated from both lung and dermis of neonatal rats and the poly(A) RNA therein was isolated by oligo(dT)-cellulose chromatography. The RNA fractions were then translated in the nuclease-treated reticulocyte lysate in the presence of radioactive proline. Optimal collagen and noncollagen protein synthesis directed by lung poly(A) RNA occurred at 0.7 mm magnesium and 100 mm potassium. The RNA fraction directed the synthesis of both proα₁ and proα₂ chains as determined by polyacrylamide gel electrophoresis. The poly(A) RNA isolated from both lung and dermis polysomes of rats treated with triamcinolone diacetate synthesized significantly less collagen peptides as determined by collagenase digestion as did the RNA isolated from polysomes of nontreated animals. Noncollagen protein synthesis was decreased to a lesser extent than collagen synthesis. Glucocorticoid treatment did not affect the ability of either polysomes in wheat germ extract or polysomal poly(A) RNA in nuclease-treated reticulocyte lysate to synthesize prolyl hydroxylase as determined by immunoprecipitation. These data indicate the glucorticoid-mediated inhibition of collagen polypeptide synthesis does not result from nonspecific effect on total cellular protein synthesis of normal fibroblasts, but a selective reduction of poly some-associated messenger RNA. Furthermore these data provide a molecular basis for selective inhibitory effect of synthetic anti-inflammatory steroids on collagen synthesis.