Distribution, propagation, and coordination of contractile activity in lymphatics

Abstract

The propagation and coordination of lymphatic contractions were studied in the mesentery of the rat small intestine using in situ microscopic observation. Indexes of lymphatic diameter were simultaneously measured at two adjacent lymphangions in spontaneously contracting lymphatics (n = 51). Diameter index, contraction frequency, and the percentage of the intersegmental contractions that were propagated and coordinated (PP) were determined at both sites. The conduction velocity of the contractile activity and the percentage of the coordinated contractions that were propagated both antegrade to the direction of lymph flow and retrograde to the flow stream were determined. The results indicate that 1) 80-90% of the lymphatic contractions in the vessels we evaluated were propagated, 2) the wave of contractile activity propagated both centrally and peripherally, and 3) the conduction velocity of the contractile activity was approximately 4-8 mm/s. We tested the hypothesis that gap junctional communication is responsible for the coordination of the contractile event. To accomplish this, we used the gap junction 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 junction blockade. These results indicate that gap junctional communication played an important role in the propagation and coordination of contractions that occurred in spontaneously active lymphatics.

Modulation of lymphatic muscle contractility by the neuropeptide substance P

“…4C). The calculation of AFP (49), rather than another index such as fractional pump flow (11), permitted the subsequent comparison of isometric and isobaric data (51). AFP peaked at a preload of ϳ0.4 mN , and Amp-Freq product (AFP; C) from 14 isometric vessels subjected to preload ramps in the absence (E) or presence (F) of SP (1⅐ 10 Ϫ8 M).…”

“…We used isolated, cannulated lymphatic vessels to distinguish between the possible direct and indirect actions of SP as defined above. We used rat mesenteric vessels because of the extensive amount of available data regarding the contractile behavior of these vessels both in vivo (2,3,49) and in vitro (11,12,51). A unique aspect of our study was to assess the action of SP on collecting lymphatic vessels under both isometric and isobaric conditions.…”

Intrinsic pump-conduit behavior of lymphangions

“…Like veins, lymphatic vessels are remarkably thin-walled and contain unidirectional valves. Whereas the initial lymphatics are typically passive structures, the conducting lymphatics contain smooth muscle that cyclically contracts at a rate of 1-15 cycles per minute (2,13,27,42,53). The section of vessel between valves forms a functional unit, called a lymphangion (32).…”

“…Cyclical contractions of lymphangions usually actively pump lymph against a local pressure gradient. The concept that lymph is actively transported by lymphatic vessels took years to be accepted (17) and has become the focus of investigators interested in the role of lymphatic function in the genesis and resolution of edema (2,4,6,25,27,42,53).…”

Lymphangiogenesis in post-natal tissue remodeling: Lymphatic endothelial cell connection with its environment

“…Gap junctions were described only in collecting vessels where these junctions play a role in the propagation and coordi-138 nation of contractions in lymphatics in the mesentery of the rat small intestine (Zawieja et al, 1993 Table 1 Mouse knock-out models and human mutations of cell-cell and cell-matrix molecules associated with a lymphatic phenotype TJs and AJs are not as frequently seen in lymphatics as in blood vessels (Leak and Burke, 1968;Pepper and Skobe, 2003). One of the feature of lymphatic capillaries is the incomplete or absence of BM (Leak and Burke, 1968).…”