INCREASE IN TONE AND INTRACELLULAR CA2+ IN RABBIT ISOLATED EAR ARTERY BY PLATELET-DERIVED GROWTH-FACTOR

1 The effect of platelet-derived growth factor (PDGF-AB) on tone and intracellular Ca2+ ([Ca2+]) was examined in rabbit isolated ear arteries. Arteries were mounted in a myograph and loaded with the Ca2+-sensitive fluorescent indicator, fura-2, for concurrent measurements of isometric force and [Ca2+](i). 2 PDGF-AB contracted rabbit ear artery in a concentration-dependent manner. PDGF-AB induced tone was associated with a rise in [Ca2+](i). In the presence of noradrenaline, PDGF-AB induced a similar rise in [Ca2+]i but contraction in response to PDGF-AB in the presence of noradrenaline was increased compared with PDGF-AB alone. 3 PDGF-AB-induced rise in [Ca2+]i and tone were abolished by removal of extracellular Ca2+ (with addition of BAPTA, a Ca2+ chelator), and by preincubation with a dihydropyridine calcium channel blocker, (-)-202 791. Bistyrphostin, a selective inhibitor of tyrosine kinases, also inhibited PDGF-AB-induced tone, but had no effect on noradrenaline- or potassium-induced tone. 4 PDGF-AB contracts rabbit ear artery by increasing Ca2+ entry through voltage-operated calcium channels. This effect involves activation of a tyrosine kinase.