TY - JOUR T1 - Lysophosphatidylcholine Potentiates Phenylephrine Responses in Rat Mesenteric Arterial Bed through Modulation of Thromboxane A<sub>2</sub> JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 355 LP - 361 DO - 10.1124/jpet.105.097964 VL - 317 IS - 1 AU - Rui Zhang AU - Brian Rodrigues AU - Kathleen M. MacLeod Y1 - 2006/04/01 UR - http://jpet.aspetjournals.org/content/317/1/355.abstract N2 - Lysophosphatidylcholine (LPC) plays important physiological and pathophysiological roles in the cardiovascular system. Despite this, there is little information about its effects on vasore-activity of resistance vessels. The present study was designed to characterize the effects of LPC in the isolated perfused rat mesenteric arterial bed (MAB) and to investigate the underlying mechanisms of the changes it produced. Perfusion with 10 μM LPC for 40 min did not significantly affect basal perfusion pressure or reactivity of MAB to the α1-adrenoceptor agonist phenylephrine (PE) but almost completely abolished the maximal endothelium-dependent relaxation to acetylcholine (Ach), reducing it from 93 ± 5 to 7 ± 4% (p &lt; 0.001). After washout of LPC for 60 min, the vasodilator response to Ach partially recovered, whereas the vasoconstrictor response to PE was markedly enhanced, the pD2 value increasing from 7.50 ± 0.04 to 8.13 ± 0.15 and maximum response to 199 ± 24% of control (p &lt; 0.001). Pretreatment with either indomethacin, a nonselective inhibitor of cyclooxygenase, or SQ-29548 [[1S-[1a,2a(Z),3a,4a]]-7-[3-[[2-[(phenylamino)carbonyl]hydrazino] methyl]-7-oxabicyclo [2.2.1]hept-2-yl]-5-heptanoic acid], a selective thromboxane receptor antagonist, completely prevented the potentiation of the PE response after washout of LPC. In untreated MABs, only the highest concentration of PE produced a significant increase in thromboxane A2 (TxA2) production (assessed by enzyme-immunoassay of thromboxane B2 levels). This was prevented by perfusion with LPC but was significantly increased after LPC washout. The basal release of TxA2 was not modified by LPC. These results demonstrate that LPC exerts both immediate and residual effects on the reactivity of the rat MAB and that these effects are at least partially due to modification of PE-induced TxA2 production. The American Society for Pharmacology and Experimental Therapeutics ER -