Regulation of protein metabolism and DNA synthesis by fibroblast growth factor in BHK-21 cells.

1. Acidic and basic fibroblast growth factors (aFGF, bFGF) were shown to inhibit protein breakdown in BHK-21 cells, with the latter exhibiting approx. 6-fold greater sensitivity. 2. The maximum response achieved was less than observed with insulin or insulin-like growth factor-1 (IGF-1), and was not additive with those growth factors over the 4 h measurement period. The inhibition of protein breakdown followed the same time course with all the growth factors tested, and was enhanced equally by NH4+ ions. Taken together, these results suggest similar mechanisms for effects of the different growth factors on protein breakdown. 3. Protein synthesis was stimulated by bFGF, insulin and IGF-1, with partial additivity evident between bFGF and the other peptides. Increases in cell-culture protein content paralleled the changes in the rate of protein synthesis. 4. DNA synthesis was stimulated more effectively in BHK-21 cells by aFGF or bFGF than by insulin or IGF-1, with partial additivity between the two groups of growth factors. 5. Since each of the growth factors independently produced both relatively rapid effects on protein metabolism and more prolonged increases in DNA synthesis, some caution is warranted before classifying them into truly distinct groups as either competence or progression factors.