Identification of hypoxanthine and inosine in brain dialyzable fraction as stimulators for growth of porcine aortic endothelial cells in response to fibroblast growth factor in either dialyzed serum media or low serum media.

The rate of proliferation of porcine aortic endothelial cells (PAEC) in response to fibroblast growth factor (FGF) was largely retarded when incubated in Dulbecco's modified Eagle's medium (DMEM) supplemented with either 1% fetal bovine serum (FBS) or 10% dialyzed FBS in place of 10% FBS. Proliferation of endothelial cells in low serum media in response to FGF was enhanced to the level of media containing FGF plus 10% FBS by the addition of the dialyzable fraction from bovine brain homogenates. From the bovine brain dialyzable fraction, two active components were purified and identified as hypoxanthine and inosine. Either hypoxanthine or inosine, at a dose of 5 microM in DMEM with 1% FBS, maximally increased the incorporation of [3H]thymidine into DNA of PAEC in low serum media in the presence of FGF. However, no additive effect was observed when hypoxanthine and inosine were added simultaneously. The present data indicate that the proliferative action of FGF on PAEC can be potentiated by hypoxanthine and inosine.