BASIC FIBROBLAST GROWTH-FACTOR STIMULATES CONNEXIN-43 EXPRESSION AND INTERCELLULAR COMMUNICATION OF CARDIAC FIBROBLASTS

Gap junctions (GJ) are membrane specializations responsible for interc ellular communication and for ensuring electrical and/or metabolic cou pling between cells. They are composed of connexins, a family of relat ed proteins. Connexin-43 (Cx43) is a major connexin of the rat heart, expressed by myocytes as well as non-muscle cells. In this communicati on we have examined expression of Cx43 by cardiac fibroblasts and regu lation of its expression by an endogenous mitogen, basic fibroblast gr owth factor (bFGF). Recombinant human bFGF, administered to cultured c ells which had been maintained in 0.5% serum for 48 h, induced dose-de pendent and statistically significant increases in Cx43 mRNA as well a s protein accumulation, at 6 h after addition. Intercellular communica tion was also increased at 6 h but not 30 min after bFGF treatment, as assessed using a scrape-loading protocol. It is concluded that the bF GF-induced stimulation of Cx43 expression caused increased coupling be tween cardiac fibroblasts. This would be of importance in injured myoc ardium, the increased bFGF content of which might stimulate electrical coupling involving fibroblasts of the scar tissue.