Substance P enhances pump function of isolated lymphatics from hemorrhagic shock rats

AIM: To establish a technique of lymphatic perfusion in vitro and to determine the effect of substance P(SP) on lymphatic contractility during the process of hemorrhagic shock(HS).METHODS: Male Wistar rats were randomly divided into control group(surgical procedure only) and HS group [the rats underwent bloodletting from femoral artery while the mean arterial pressure was maintained at(40±2) mmHg,and were further divided into 5 subgroups: shock 0 h,0.5 h,1 h,2 h and 3 h groups].Thoracic ducts were isolated from HS rats at the corresponding time points.The segment of thoracic duct was prepared,perfused in vitro at the transmural pressure of 3 cmH2O and stimulated with gradient concentrations of SP to measure the lymphatic contractile activity.The end-systolic diameter,end-diastolic diameter,contraction frequency(CF) and passive diameter of isolated lymphatics were measured.The contraction amplitude(CA),tonic index(TI) and fractional pump flow(FPF) were also calculated.RESULTS: SP increased lymphatic CF,TI and FPF,and the effects were enhanced with the increase in the concentration of SP.The CF,TI and FPF of 2 h-and 3 h-shocked lymphatics were elevated to/over the value of baseline levels before the experiment by SP at the concentration starting from 3×10-8 mol/L.At the same concentration of SP,the CA of lymphatics showed no significant statistical difference among the groups.However,with the increase in SP concentration,the lymphatic CA had a downward trend in all groups.CONCLUSION: SP enhances the pump function of lymphatics not only under physiological condition,but also in shock during different stages.