On the basis of previous experiments, we have proposed a model in which defects in collagen and proteoglycan synthesis in scurvy are caused indirectly by ascorbate deficiency. We suggested that the decreases were caused by changes in humoral factors during scurvy-induced fasting, rather than through the role of ascorbate in the biosynthetic pathway of either of these components. It had been assumed previously that defective connective tissue metabolism in this disease was due to defective proline hydroxylation and procollagen secretion. The results of our current studies provide additional support for our model. They show that there are changes in hormones and growth factors in the serum of scorbutic guinea pigs during the period when the animals are in a fasting state which are similar to changes in fasted animals and humans with no ascorbate deficiency. The exposure of normal cartilage chondrocytes to such scorbutic serum, with supplementation of ascorbate, resulted in decreased synthesis of extracellular matrix components. The collagen synthesized had normal levels of hydroxyproline. We conclude that the growth promoting activity of vitamin C in vivo is mediated initially through reactions other than those directly involved in connective tissue metabolism. In a second study, we have found that the collegan phenotype of a 4-nitroquinoline-1-oxide transformed line of Syrian hamster embryo (SHE) fibroblasts, NQT-SHE, was markedly altered from that of normal SHE cells, which synthesized mainly type I procollagen, (proAlpha 1)2 pro alpha 2. Total collagen synthesis in the transformant was reduced to about 30% of the control level primarily because synthesis of one of the two subunits of type I procollagen, pro alpha 1(I), was completely suppressed. The major collagenous products synthesized consisted of two polypeptides, designated as N-33 and N-50, which could be completely separated by precipitation with ammonium sulfate at 33% and 50% saturation, respectively. Results of peptide mapping and other experiments indicate the N-collagens are altered pro alpha 2(I) chains and that they differ from each other.
