Li B, Silver I, Szalai J P, Johnston M G
Department of Laboratory Medicine and Pathobiology, Sunnybrook Health Science Centre, University of Toronto, 2075 Bayview Avenue, Toronto, Ontario, M4N 3M5, Canada.
Microvasc Res. 1998 Sep;56(2):127-38. doi: 10.1006/mvre.1998.2089.
We applied the principles of cardiac mechanics to study the contraction cycles of postnodal sheep mesenteric lymphatic vessels in an in situ preparation. A segment of intestinal lymphatic was isolated from lymph input and provided with Krebs solution from a reservoir. Pressure-volume relationships were assessed under various transmural pressure conditions using videomicroscopic techniques to measure diameter changes and a miniature catheter pressure transducer to monitor intralymphangion pressure. The contraction cycles were quite variable but, on average, exhibited three phases of systole and three phases of diastole with periods of isovolumetric contraction and relaxation. Elevations of transmural pressure up to 4 cm H2O resulted in significant increases in stroke volume, ejection fraction, pulse pressure, and output/minute but not contraction frequency. Regression analysis of the end systolic (ESPVR) and end diastolic pressure-volume relations (EDPVR) revealed a linear ESPVR (r2 = 0.83 +/- 0.03) and exponential EDPVR (r2 = 0.83 +/- 0.02), a result that is similar to that observed in cardiac contraction cycles. Following a 25% whole blood volume bleed (a stimulus known to enhance lymphatic pumping), significant increases in stroke volume, ejection fraction, and output/minute were observed up to transmural pressures of 4 cm H2O. While an index used to assess cardiac contractility (end systolic elastance-Ees) was not observed to change after the bleed, a shift to the left of the end-systolic pressure-volume relations compared with the sham-bled group (significant shift of regression lines for ESPVR) suggested that hemorrhage exerted a positive inotropic effect on mesenteric lymphatics.
我们应用心脏力学原理，在原位制备中研究节后绵羊肠系膜淋巴管的收缩周期。从淋巴输入处分离出一段肠淋巴管，并从储液器中提供 Krebs 溶液。使用视频显微镜技术测量直径变化，并使用微型导管压力传感器监测淋巴管内压力，在各种跨壁压力条件下评估压力 - 容积关系。收缩周期变化很大，但平均而言，呈现三个收缩期和三个舒张期，伴有等容收缩和舒张期。跨壁压力升高至 4 cmH₂O 导致每搏输出量、射血分数、脉压和每分钟输出量显著增加，但收缩频率不变。对收缩末期（ESPVR）和舒张末期压力 - 容积关系（EDPVR）的回归分析显示，ESPVR 呈线性（r² = 0.83 ± 0.03），EDPVR 呈指数关系（r² = 0.83 ± 0.02），这一结果与在心脏收缩周期中观察到的结果相似。在进行 25% 全血容量失血（已知该刺激可增强淋巴泵血）后，在跨壁压力达到 4 cmH₂O 之前，观察到每搏输出量、射血分数和每分钟输出量显著增加。虽然在失血后未观察到用于评估心脏收缩性的指标（收缩末期弹性 - Ees）发生变化，但与假手术组相比，收缩末期压力 - 容积关系向左移位（ESPVR 回归线有显著移位），表明出血对肠系膜淋巴管产生了正性肌力作用。
