Platelet-derived growth factor causes endothelium-independent relaxation of rabbit mesenteric artery via the release of a prostanoid.

Recent evidence has indicated that the mitogen platelet-derived growth factor (PDGF) can act acutely to regulate arterial tone. In this study we demonstrate that the BB isoform of PDGF (PDGF-BB) can cause endothelium-independent relaxation of rabbit isolated mesenteric arteries. In endothelium-denuded arteries, PDGF-BB (40 pM - 8.0 nM) caused concentration-dependent relaxation of noradrenaline-induced tone. The relaxation to PDGF-BB was abolished by a cyclo-oxygenase inhibitor, indomethacin (10 microM) and by the PDGF receptor-associated tyrosine kinase inhibitor, tyrphostin AG1295 (50 microM), but not by N:(G)-monomethyl-L-arginine (L-NMMA, 200 microM), an inhibitor of nitric oxide (NO) synthase. PDGF-BB (4.0 nM) significantly increased the release of prostacyclin (PGI(2)) in endothelium-denuded arteries. Exogenously applied iloprost (1 microM), a stable analogue of PGI(2), relaxed the endothelium-denuded artery. PDGF-BB (4.0 nM) significantly increased the cyclic AMP content. In the absence of Ca(2+), PDGF-BB (4.0 nM) failed to relax the artery, and the release of PGI(2) was almost completely suppressed. In addition, the release of PGI(2) by PDGF-BB (4.0 nM) was significantly reduced in the presence of endothelium. The effect of endothelium was eliminated by L-NMMA (200 microM) and PGI(2) release increased. These data indicate that in rabbit mesenteric arteries, PDGF-BB can evoke endothelium-independent relaxation by stimulating the synthesis of PGI(2). The PDGF-BB-induced prostaglandin synthesis is dependent on both Ca(2+) and tyrosine phosphorylation of the PDGF receptor, and is attenuated by endothelium-derived NO.