CATECHOLAMINE-MEDIATED LYMPHATIC CONSTRICTION - INVOLVEMENT OF BOTH ALPHA-1-ADRENOCEPTORS AND ALPHA-2-ADRENOCEPTORS

It has been proposed that catecholamines may regulate lymphatic function by altering lymphatic resistance. In this study we perfused lymphatics in the paw of the anesthetized dog, administering catecholamines intralymphatically before and during intra-arterial administration of adrenoreceptor antagonists. Epinephrine and norepinephrine both increased lymphatic perfusion pressure. When the infusions were repeated during intra-arterial phentolamine, neither catecholamine significantly altered lymphatic perfusion pressure, thus implicating lymphatic adrenoreceptors. Intralymphatic infusion of these catecholamines during the intra-arterial infusion of prazosin significantly increased lymphatic perfusion pressure, but the increase was markedly less than that seen prior to prazosin. In these same animals, the lymphatic constriction produced by intralymphatic phenylephrine was completely blocked, indicating an effective blockade of the alpha-1-receptors. The intralymphatic infusion of phenylephrine or alpha-methylnorepinephrine both significantly increased lymphatic perfusion pressure, confirming the presence of both alpha-1- and alpha-2-receptors. These data demonstrate that the prenodal lymph vessels of the canine fore-limb contain both alpha-1- and alpha-2-receptors and that epinephrine and norepinephrine interact with both classes of receptors to produce lymphatic constriction.