Estrogen treatment enhances mesenteric lymphatic contractility in rats after hemorrhagic shock

AIM To investigate the effects of 17β-estradiol （E2） treatment on the mesenteric lymphatic microcirculation and isolated lymphatic contractility in rats after hemorrhagic shock， and to explore the relationship between contractility and the difference between intra- and extracellular calcium ion concentrations （［Ca²⁺］） of lymphatic smooth muscle cells （LSMCs）. METHODS Male Wistar rats were divided into sham group， shock group and shock+E2 group. The rats were subjected to hemorrhage ［（40±2） mmHg for 90 min］ and resuscitation with or without subcutaneous injection of E2 （2 mg/kg）. After resuscitation for 3 h， the mesenteric lymphatic microcirculation in vivo was observed. Moreover， the isolated mesenteric microlymphatic rings were prepared for the observations of lymphatic contractility evaluated by the indexes including end-systolic diameter， end-diastolic diameter， contraction frequency （CF） and passive diameter. Meanwhile， the difference between intra- and extracellular ［Ca²⁺］ of LSMCs was recorded during lymphatic contraction. RESULTS Treatment with E2 significantly enhanced the CF， total contractile fraction and lymphatic dynamics index in vivo in the rats after hemorrhagic shock， and increased the CF， the fractional pump flow and the difference between intra- and extracellular ［Ca²⁺］ of LSMCs in isolated lymphatics from the shocked rats （P<0.05）. CONCLUSION Estrogen treatment enhances lymphatic contractility in rats after hemorrhagic shock， which is related to enhancement of difference between intra- and extracellular ［Ca²⁺］ of LSMCs.