Receptor mechanisms of PAF mediated lymphatic constriction in the canine forelimb.

Platelet activating factor (PAF) is a potent inflammatory lipid. In this study we assessed the ability of PAF to impact lymphatic vessel function by altering prenodal lymphatic resistance. Intralymphatic PAF (7.47 x 10(-6), 7.47 x 10(-5) and 7.47 x 10(-4) M) increased lymphatic perfusion pressure at the two highest infusion rates. PAF mediated lymphatic constriction was not altered by the intra-arterial infusion of phentolamine but was blocked by the intra-arterial infusion of the PAF receptor antagonist WEB 2170. These data indicate that in addition to PAF's effects on microvascular permeability, this agent may also impact the ability of the lymphatics to transport fluid through alterations in lymphatic smooth muscle tone. PAF mediated lymphatic constriction is not mediated by alpha-receptors but rather through PAF receptor mediated mechanism.