title: Ascorbate deficiency results in decreased collagen production: under-hydroxylation of proline leads to increased intracellular degradation.
abstract: 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 microgram/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.
mesh_terms: D001205:Ascorbic Acid / Q000494:pharmacology; D001206:Ascorbic Acid Deficiency / Q000378:metabolism*; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D006909:Hydroxyproline / Q000378:metabolism; D007700:Kinetics; D008168:Lung / Q000378:metabolism*; D011392:Proline / Q000378:metabolism*
chemical_list: D003094:Collagen; D011392:Proline; D001205:Ascorbic Acid; D006909:Hydroxyproline