The role of the microlymphatic valve in the propagation of spontaneous rhythmical lymphatic motion in rat.

Male Wistar rats (n = 12) with the mesenteric preparation were used to quantitatively investigate the characteristics of wave-like propagation of spontaneous rhythmical lymphatic motion and to explore the mechanism of microlymphatic valve on the activity of lymphatic motion. The dynamical behaviors of collecting lymphatics were visualized by a closed circuit TV system. The frequency, amplitude, and phase angle of the diameter oscillation, the spreading speed of peristaltic wave and the contractile index (CI) of rhythmical lymphatic motion were measured and calculated by the image processing system. The lymphatic segment between two adjacent valves, named by lymphangion, was a basic unit of microlymphatic activity. The present results revealed that there was a wave-like propelling of the contractile activity progressively from one lymphangion to the next. No significant characteristic differences were observed from the two adjacent lymphangion units except the increasing contractile index. The motion wave propagation from upstream over a valve to down stream led to a significant phase angle change. The pacemaker site of lymphatic motion seemed to be at the inlet side of the valve in each lymphangion unit. The contractile motion wave propagated just within each lymphangion unit. The lymph flow over the valve converted the pressure changes between two adjacent lymphangions and stimulated a new contraction wave at the next inlet site of valve. The endothelium response to wall tension and shear stress alteration near the inlet valve site might be one of the pacemaking mechanisms of lymphatic motion.