Active and passive mechanical characteristics of bovine mesenteric lymphatics

Abstract

Pressure-volume and pressure-radius relationships in lymphangions isolated from bovine mesenteric lymphatics were similar in pattern with those in the vein. Circumferential modulus of elasticity of the lymphatics ranged from 4.2 x 10(4) tatic walls. The contractile force increased in early stages of distension and decreased after an optimal intraluminal pressure was attained. The spontaneous activity was also affected by the rate of wall deformation. The pacemaker site of spontaneous activity seemed to be in the wall in the immediate vicinity of the inlet valve of a lymphangion. The activity propagated with a velocity of 4-5 mm/s. Ejection fraction of a lymphangion was between 45 and 65%. The endurance limit of the lymphatic valve was 68.4 +/- 7.6 cmH2O in specimens of about 3 mm in outer diameter. These findings suggested that lymphatic smooth muscle seemed to play a major role in elastic behavior of the wall and in regulation of the spontaneous activity, thereby affecting significantly passive and active lymph transport.

Passive Pressure–Diameter Relationship and Structural Composition of Rat Mesenteric Lymphangions

“…Our pressure-diameter curves are qualitatively similar to the findings of Ohhashi et al, 10 who performed pressureradius and pressure-volume tests on bovine mesenteric lymphatics, and observed higher distensibility at lower luminal pressures. Our results suggest that normal operating pressures for a lymphatic vessel are between 0 and 5 cmH 2 O and that lymphatic vessels become effectively indistensible conduits at pressures greater than 5 cmH 2 O.…”

“…Our results suggest that normal operating pressures for a lymphatic vessel are between 0 and 5 cmH 2 O and that lymphatic vessels become effectively indistensible conduits at pressures greater than 5 cmH 2 O. The stiffness transition at this threshold was sharper than that seen by Ohhashi et al 10 in larger vessels and a different species. Venugopal et al 11 used the latter data in fitting a combination of two straight lines to the pressure-volume relationship of a relaxed lymphangion.…”

“…There have been few attempts at characterizing the mechanical properties of lymphangions. Most have been in larger vessels (0.5-3 mm in diameter), and analysis has been more or less qualitative (e.g., Ohhashi et al 10 ). None have developed a constitutive equation or related the mechanical behavior to structural components.…”

“…Ohhashi et al 10 studied the active and passive mechanical properties of bovine mesenteric lymphatics (vessel diameter *3 mm) via a series of pressure-volume and pressureradius relations. Their findings suggested that smooth muscle cells play a role in the elastic behavior of the lymphangion by increasing the elastic modulus (i.e., stiffening of vessel).…”

Aged Lymphatic Contractility: Recent Answers and New Questions

“…The transmural pressure/stretch-dependent modulation of lymphatic contractility is one of the principle regulatory mechanisms of lymphatic pumping that serves a goal to adapt lymphatic transport to the different lymphatic preloads. [5][6][7][8][9][10] The alterations in stretch-related regulatory mechanisms in 24-mo old segments indicate that both pacemaking and contractile machinery are involved in age-related changes of active lymph pump in rat TD. Lowered lymphatic tone in aged TD segments, together with decreased lymphatic contraction amplitude, may be considered an indicator of age-related weakening of muscle cells and their diminished ability to create enough force to maintain the level of tone and contractile force appropriate to the lymphatic preloads.…”