Influence of cell cycle on collagen synthesis by human gingival fibroblasts

Abstract

The effect of cell cycle stages on collagen and protein synthesis by human gingival fibroblasts was investigated. The fibroblasts were synchronized by depriving them of serum for 48 hours and then activating them to divide by adding 10 per cent fetal calf serum. At various time points, the cells were pulse labeled with radioactive proline, and protein and collagen synthesis were measured. Proteins were quantitated by total proline incorporation and collagen was assayed by digesting it with purified bacterial collagenase. Protein synthesis increased with time and reached maximal levels at and after 24 hours, the time of peak DNA synthesis. The proportion of collagen synthesized also increased, and it reached maximum values after 33 hours. The levels of transport of proline into the cell did not parallel the protein synthesis. Confluent and nonconfluem cells gave similar results. The ratio of collagen type I to type III collagen did not significantly vary at any time and no new collagens were detected.