[Effect of a medium with a low serum content on protein synthesis and secretion and RNA and DNA synthesis in a skin fibroblast culture from patients with rheumatoid arthritis and systemic scleroderma].

Synthesis and secretion of protein, as well as synthesis of RNA and DNA by skin fibroblasts of patients with systemic sclerodermia (SSD) and rheumatoid arthritis (RA) upon prolonged culturing of fibroblasts in the medium with low (0.5-1%) serum content differ markedly in their direction and intensity from protein, RNA and DNA synthesis by skin fibroblasts of healthy donors (HD) and by fetal fibroblasts. It has been found that skin fibroblasts of patients with RA and SSD, as well as those of HD, secrete 75-80% of protein synthesized by fibroblasts de novo upon their culturing in DMEM medium with 1% human serum. Under the same conditions, on days 2-5 of culturing, RNA synthesis in the fibroblasts of patients with RA and SSD was increased 3-4-fold, while DNA synthesis was increased 2-3-fold. Collagenolytic and caseinolytic activity in the culture medium of skin fibroblasts from HD and patients with RA reached maximal levels on days 3-5. High protein secretion was observed in DMEM serum-free medium in the presence of vitamin mixture upon culturing skin fibroblasts of patients with SSD. The results obtained show that skin fibroblasts from HD differ in their functional activity from those of patients with rheumatic disorders. It might be suggested, therefore, that the mechanism of protein secretion plays an important role in the maintenance of constant intracellular protein levels in resting cells.