Our previous studies provided evidence that guinea pigs that are vitamin C deficient and those that have been fasted, but supplemented with vitamin C, are equivalent with respect to the mechanisms responsible for decreased collagen and cartilage proteoglycan synthesis. Sera from both groups contain a circulating factor that inhibited DNA synthesis in 3T3 cells and collagen and proteoglycan synthesis in cultured primary chondrocytes and adult human skin fibroblasts. The presence of the inhibitor in fasted and scorbutic sera was correlated with (30-50 kDa) that can an increase in low molecular weight IGF-I binding proteins inhibit binding of IGF-I to its receptor on 3T3 cells and human fibroblasts. A 30 kDa binding protein was increased in both scurvy and fasting while a 36 kDa binding protein appeared to be uniquely induced by vitamin C deficiency. 4-Nitroquinoline-l-oxide transformed Syrian hamster embryo fibroblasts (NQT-SHE) do not synthesize the pro 1 (I) subunit of type I procollagen but continue to synthesize altered forms of the other subunit, pro 2(I). The level of poly A+ pro 1(1) mRNA is approximately 1% of the level in normal hamster primary fibroblasts and 10% of the level in a normal hamster fibroblast line (BHK). These levels of the mRNA should lead to detectable synthesis of the pro l(I) chain, which suggests that the mRNA cannot be translated into protein. In vitro nuclear run-off transcription assays showed that the rates of transcription of the pro 1(I) gene in nuclei from NQT-SHE cells was similar to that in the normal BHK fibroblasts, suggesting that the low steady state level of pro 1(I) mRNA in NQT-SHE fibroblasts is not caused by a defect in transcription. Thus, the failure of NQT-SHE cells to synthesize the pro 1(I) polypeptide may result from multiple defects in the transcription to translation pathway.
