Isoelectric focusing of macrophage culture media and the effect of the fractions on the synthesis of DNA and collagen by fibroblasts.

Macromolecules from rat peritoneal macrophage culture media were separated into 30 fractions by flat bed isoelectric focusing (IEF). The fractions were tested for their influence on thymidine and proline incorporation into cultured rat granuloma fibroblasts. Three fractions, stable after freezing and lyophilization, were of interest: one inhibiting thymidine incorporation (focusing at pH 7.3-7.6), another stimulating thymidine incorporation (focusing at pH 4.4-5.3), and the third stimulating proline incorporation into cells and medium collagen (focusing at pH 10.2-10.7). The last also exhibited a ribonuclease (RNase) activity with a pH-optimum of 7.0-7.5.