Fibronectin synthesis and degradation in human fibroblasts with aging.

Fibronectin was measured in early and late passaged human skin fibroblasts utilizing immunoprecipitation and polyacrylamide gel electrophoresis. A progressive increase in the rate of fibronectin and total cellular protein synthesis per cell was observed by late passaged human diploid fibroblasts. The absolute protein concentration increased in the late passaged fibroblasts. There was no significant difference in the [3H]leucine incorporation into fibronectin or total cellular protein/mg protein. The turnover of fibronectin and total cellular protein did not differ between early and late passaged fibroblasts. The transport of fibronectin to the cell membrane was similar in late passaged fibroblasts. The increased fibronectin synthesis in senescent fibroblasts appeared to correlate with the general increase in rate of protein synthesis/cell.