Relationship Between the Dose of Ascorbic Acid and its Structural Analogs and Proline Hydroxylation in Various Biological Systemst

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Abstract
The effect of ascorbic acid on the rate of in vitro collagen formation was examined in several guinea pig tissues having different rates of collagen metabolism and in chick embryo skin after various conditions of ascorbic acid supplementation. It was found that in embryonic skin, carrageenan granuloma and liver the extent of C14-hydroxyproline forniation was markedly influenced by the amount of ascorbic acid present in the tissue, which, in turn, reflected the dose of ascorbic acid administered in vitro. The increase of collagen synthesis above the normal rate was directly proportional to the increase in concentration of ascorbic acid in the tissue. This was observed not only in tissues from animals dependent on an exogenous supply of ascorbic acid but also in tissues from organisms capable of ascorbic acid synthesis. However, the rate of collagen synthesis was not affected by ascorbic acid in organs which normally exhibit a low metabolic turnover of collagen (lung, muscle); in these collagen synthesis was found to be independent of the amount of available ascorbic acid. The presence of additional ascorbic acid in the incubation medium had a stirnulatory effect on collagen synthesis in chick embryo skin and carrageenan granuloma, but this immediate effect was less pronounced than that of the endogenous ascorbic acid, elevated by in viao supplementation. It is suggested that the stimulatory effect of ascorbic acid on collagen synthesis may be dependent on the availability of the precursor form of proline hydroxylase. Comparison of the in vitro and in vivo effect of some ascorbic acid analogs upon proline hydroxylation in carrageenan granuloma from scorbutic guinea pigs indicates that although some of the derivatives were effective in vitro, their efficiency in vivo was not comparable to the effect of L-ascorbic acid. Using the measure of radioactivity of ultrafilterable hydroxproline as an index of collagen degradation, it was found that ascorbic acid deficiency did not accelerate degradation of collagen which had been hydroxylated.