Ascorbate deficiency results in decreased collagen production: Under-hydroxylation of proline leads to increased intracellular degradation

• Published in: Archives of biochemistry and biophysics Vol. 226; no. 2; pp. 681 - 686
• Main Authors: Berg, Richard A., Steinmann, Beat, Rennard, Stephen I., Crystal, Ronald G.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.10.1983
• Subjects: Ascorbic Acid - pharmacology; Ascorbic Acid Deficiency - metabolism; Cells, Cultured; Collagen - biosynthesis; Collagen - metabolism; Fibroblasts - drug effects; Fibroblasts - metabolism; Humans; Hydroxyproline - metabolism; Kinetics; Lung - metabolism; Proline - metabolism
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1016/0003-9861(83)90338-7

Collagen production by cultured human lung fibroblasts was examined when the cells were made deficient in ascorbate. Cells grown in the absence of ascorbate produced 30% less collagen during a 6-h labeling period than cells incubated with as little as 1 μg/ml ascorbate during the labeling period. Cells grown without ascorbate produced under-hydroxylated collagen which was subject to increased intracellular degradation from a basal level of 16% to an enhanced level of 49% of all newly synthesized collagen. The likely mechanism for increased intracellular degradation is the inability of under-hydroxylated collagen to assume a triple-helical conformation causing it to be susceptible to intracellular degradation. Measurement of collagen production by enzyme linked immunoassay (ELISA) using antibodies directed against triple-helical determinants of collagen showed that both types I and III collagens were affected. In contrast, another connective tissue component, fibronectin, was not affected. Analysis by ELISA showed a greater decrease in collagen production than did analysis by the collagenase method, suggesting that some non-helical collagen chains (detected by collagenase but not by ELISA) were secreted in the absence of ascorbate. These results provide a mechanism to account, in part, for the deficiency of collagen in connective tissues which occurs in a state of ascorbate deficiency.