DISTRIBUTION, PROPAGATION, AND COORDINATION OF CONTRACTILE ACTIVITY IN LYMPHATICS

The propagation and coordination of lymphatic contractions were studie d in the mesentery of the rat small intestine using in situ microscopi c observation. Indexes of lymphatic diameter were simultaneously measu red at two adjacent lymphangions in spontaneously contracting lymphati cs (n = 51). Diameter index, contraction frequency, and the percentage of the intersegmental contractions that were propagated and coordinat ed (PP) were determined at both sites. The conduction velocity of the contractile activity and the percentage of the coordinated contraction s that were propagated both antegrade to the direction of lymph flow a nd retrograde to the flow stream were determined. The results indicate that 1) 80-90% of the lymphatic contractions in the vessels we evalua ted were propagated, 2) the wave of contractile activity propagated bo th centrally and peripherally, and 3) the conduction velocity of the c ontractile activity was approximately 4-8 mm/s. We tested the hypothes is that gap junctional communication is responsible for the coordinati on of the contractile event. To accomplish this, we used the gap junct ion blockers n-heptanol and oleic acid. PP was 90 +/- 4% under normal conditions and fell to a minimum value of 55 +/- 7% during the gap jun ction blockade. These results indicate that gap junctional communicati on played an important role in the propagation and coordination of con tractions that occurred in spontaneously active lymphatics.