Endothelin Modulation of Pumping Activity in Bovine Mesenteric Lymphatic Vessels

We studied the effects of endothelin family peptides on the pumping responses of lymphatic vessels, the receptors involved and whether vessel-derived endothelin played a role in the myogenic response to changes in transmural pressure. Postnodal bovine mesenteric lymphatics were suspended in an organ bath preparation with both inflow and outflow ends cannulated. Input to the ducts was provided from a reservoir filled with Krebs solution. With a 6 cm H2O fixed transmural pressure applied to the vessels to initiate spontaneous contractions, ET-1, ET-2 and ET-3 (tested between 10−10 and 10−8PM) depressed lymphatic pumping in a concentration-dependent fashion with the order of potency being ET-1 = ET-2 > ET-3. The concentrations of ET-1 and ET-2 that depressed pumping 50% were 0.96 × 10−9M and 0.95 × 10−9M respectively. Similarly, when transmural pressures were varied in 2 cm H2O increments between 0 and 14 cm H2O, ET-1 at 10−9 and 10−8M significantly depressed fluid pumping at the majority of distending press...