Myogenic constriction and dilation of isolated lymphatic vessels

Abstract

Davis MJ, Davis AM, Ku CW, Gashev AA. Myogenic constriction and dilation of isolated lymphatic vessels. Am J Physiol Heart Circ Physiol 296: H293-H302, 2009. First published November 21, 2008 doi:10.1152/ajpheart.01040.2008.-We tested the hypothesis that lymphatics would exhibit myogenic constrictions and dilations to intraluminal pressure changes. Collecting lymphatic vessels were isolated from rat mesentery, cannulated, and pressurized for in vitro study. The lymphatic diameter responses to controlled intraluminal pressure steps of different magnitudes were tested in the absence and presence of the inflammatory mediator substance P, which is known to enhance lymphatic contractility. Myogenic constriction, defined as a time-dependent decrease in end-diastolic diameter over a 1-to 2-min period following pressure elevation (after initial distension), was observed in the majority of rat mesenteric lymphatic vessels in vitro and occurred over a relatively wide pressure range (1-15 cmH 2O). Myogenic dilation, a time-dependent rise in end-diastolic diameter following pressure reduction, was observed in over half the vessels equilibrated at a low baseline pressure. Myogenic constrictions were independent of the cardiac-like and time-dependent compensatory decline in end-systolic diameter and increase in amplitude observed in almost all vessels following pressure elevation. Substance P increased the percentage of vessels exhibiting myogenic constriction, the magnitude and rate of constriction, and the pressure range over which constriction occurred. Our results demonstrate that myogenic responses occur in collecting lymphatic vessels and suggest that the response may aid in preventing vessel overdistension during inflammation/edema.

The contribution of K+ channels to human thoracic duct contractility

“…It is interesting, however, that the BK channel is not involved in the regulation of contraction amplitude or baseline tension. In both wire and pressure myographs, lymphatic vessels have, in a similar fashion to some arteries, an active component in addition to passive tension in the vessel wall due to stretch (7,15). In arteries, myogenic tone is partly regulated by BK channels (4), but our wire myograph data do not support that this is the case for lymphatic vessels.…”

Postinfarction healing dynamics in the mechanically unloaded rat left ventricle

“…First, it is well known that sympathetic sprouting is important for infarct healing and scar formation, especially in angiogenesis and lymphangiogenesis (3,4,20), whereas the murine HTx preparation is devoid of innervation and lacks communication with cervical ganglions and the central nervous system. Therefore, its potential impact on the inflammatory response and on cardiac neural stem cell function (10) during LV unloading cannot be clarified in the present work.…”

Anatomy and roles of lymphatics in inflammatory diseases

“…Simultaneously, lymphatics exhibit tonic contraction resembling myogenic responses in arterioles, which regulate lymphatic vessel diameter, vessel compliance and resistance. [80][81][82] Although phasic lymphatic muscle contraction within lymphangions is responsible for the propulsive lymph flow into downstream segments, tonic contraction is believed to participate in maintaining the vascular tone and integrity. Phasic contraction of lymphangions in response to distension is the primary pump mechanism, which ejects lymph into downstream collecting lymphatics.…”

“…Although vessel tone is lower in lymphatics than in blood vessels, lymphatics can increase their tonic contraction by up to 16% (change in diameter) in response to flow, environmental and pharmacological stimuli. 80,83 Within non-contracting but valve bounded collecting lymphatics, vessel tone might also maintain vascular radius permitting apposition of lymphatic valve leaflets to maintain unidirectional lymph flow. It is possible that if sufficient tonic vessel contraction is not maintained, valve sealing might not occur, leading to lymphostasis/reflux.…”