OBJECTIVETo observe the change of lymphatic reactivity to substance P (SP) during the process of hemorrhagic shock (HS) with a technique of lymphatic perfusion in vitro in this study.

METHODSMale Wistar rats were randomly divided into control group (surgical procedure only) and HS group (the rats in this group were further divided into five subgroups: shock 0 h, 0.5 h, 1 h, 2 h and 3 h groups after duplicating the HS model with method of bloodletting to mean arterial blood pressure was 40 mmHg through the femoral venous). Thoracic ducts were separated from HS rats at the corresponding time points in each group. A segment of thoracic duct was pressed and perfused in vitro at transmural pressure of 3 cm H2O, and then stimulated with gradient SP respectively. The end systolic diameter, end diastolic diameter, contraction frequency (CF) and passive diameter of isolated lymphatics were measured, while the contraction amplitude (CA), tonic index (TI) and fractional pump flow (FPF) were calculated, and the different values between pre- and post- administration of SP of CF, CA, TI and FPF were calculated and expressed as Delta CF, Delta TI, Delta CA and Delta FPF to further assess the reactivity of lymphatics.

RESULTSAfter SP incubation, the Delta CF, Delta TI, Delta CA and Delta FPF of 0 h- and 0.5 h shocked lymphatics were significantly increased when compared with that of control group on one or several concentrations. The Delta CF (at 3 x 10(-7) mol/L of SP) and Delta TI (1 x 10(-7) mol/L) of 2 h- shocked lymphatics and the Delta CF (1 x 10(-7) mol/L, 3 x 10(-7) mol/L), Delta TI (1 x 10(-7) mol/L) and Delta CA (1 x 10(-7) mol/L) of 3 h- shocked lymphatics were all significantly reduced when compared with control group.

CONCLUSIONThe reactivity of lymphatics to SP presented a biphasic change during the process of HS: increase in early phase and decline in later stage.