[Cultured myocardial cell growth and hypertrophy by basic fibroblast growth factor].

Basic fibroblast growth factor (bFGF) is a mitogen that is thought to play a important role in myocyte growth. In previous work, we found the increase of immunoreactivity of bFGF in cardiac myocyte of young SHR and pressure over loaded rat heart, and it suggested that endogenous bFGF which contained high molecular form of bFGF contributes to myocardial hypertrophy. To examine this hypothesis, rhabdomyosarcoma (A 204 cells) derived bFGF was used as wild type bFGF. Extracted bFGF from A 204 cells and nonserum conditioned medium of A 204 cells included high molecular form (22, 24 kd), as well as low molecular (18 kd) bFGF by western blotting, and showed hypertrophic effect in cultured myocardial cells. The hypertrophic effects were indicated in remarkable enlargement of cell size and significant increase in phenylalanine incorporation (x 2.2). The maximum expression of c-myc mRNA by A 204 conditioned medium was observed 30 min after stimulation, and it was also accompanied by an increase of accumulation of alpha skeletal actin mRNA by primer extension. After absorption of heparin binding growth factor from A 204 conditioned medium, it indicated no hypertrophic effects. In conclusion, it is likely that wild type bFGF including high molecular weight form plays a important role in cardiac myocyte growth and hypertrophy.