STIMULATION OF P2Y RECEPTORS ACTIVATES C-FOS GENE-EXPRESSION AND INHIBITS DNA-SYNTHESIS IN CULTURED CARDIAC FIBROBLASTS

Objectives: The aims of this study were to determine (1) whether neona tal rat cardiac fibroblasts (CAFB) express P2Y receptors; (2) whether CAFE respond to extracellular ATP by inducing expression of c-Sos mRNA ; and (3) whether extracellular ATP modulates norepinephrine (NE)-stim ulated cell growth in CAFE. Methods: Expression of P2Y(1) and P2Y(2) r eceptors and induction of c-Sos were examined by Northern blot analysi s. CAFB growth was assessed by measuring [H-3]thymidine incorporation and DNA content. P2Y receptor pharmacology was studied using various A TP analogues. Results: Northern blot analysis of polyA enriched RNA co nfirmed that at least 2 subtypes of P2Y receptors (P2Y(1) and P2Y(2)) an expressed in cultured CAFE. Extracellular ATP induced the expressio n of c-foss mRNA through a pathway that was sensitive to inhibitors of protein kinase C (PKC), but not to inhibitors of intracellular Ca2+ s ignaling. Extracellular ATP inhibited the NE-stimulated increases in D NA content and in [3H]thymidine incorporation into DNA. Whereas the po tency order for stimulation of c-fos expression was ATP = UTP > ADP > adenosine, the potency order to inhibit the NE-induced increase of [H- 3]thymidine incorporation into DNA was ATP > ADP > UTP > adenosine. Co nclusions: These data demonstrate that CAFE express both P2Y(1) and P2 Y(2) receptor mRNA and that CAFE respond to P2Y receptor stimulation b y induction of c-fos and inhibition of DNA synthesis. These findings s uggest that the effects of ATP on [H-3]thymidine incorporation into DN A and on expression of c-Sos mRNA are exerted via distinct P2Y recepto r subtypes. (C) 1998 Elsevier Science B.V.