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This Article Full Text Full Text (PDF) All Versions of this Article: 295/3/H1182    most recent 00369.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Moriondo, A. Articles by Negrini, D. Search for Related Content PubMed PubMed Citation Articles by Moriondo, A. Articles by Negrini, D.

Kinetics of fluid flux in the rat diaphragmatic submesothelial lymphatic lacunae

Dipartimento di Scienze Biomediche Sperimentali e Cliniche, Università degli Studi dell'Insubria, Varese, Italy

Submitted 9 April 2008 ; accepted in final form 10 July 2008

The specific role of loops and/or linear segments in pleural diaphragmatic submesothelial lymphatics was investigated in seven anesthetized, paralyzed, and mechanically ventilated rats. Lymphatic loops lay peripherally above the diaphragmatic muscular plane, whereas linear vessels run over both the muscular and central tendineous regions. Lymph vessel diameter, measured by automatic software analysis, was significantly greater (P < 0.01) in linear vessels [103.4 ± 8.5 µm (mean ± SE), n = 18] than in loops (54.6 ± 3.3 µm, n = 21). Conversely, the geometric mean of intraluminal flow velocity, obtained from the speed of distribution of a bolus of fluorescent dextrans injected into the vessel, was lower (P < 0.01) in linear vessels (26.3 ± 1.4 µm/s) compared with loops (51.3 ± 3.2 µm/s). Lymph flow, calculated as the product of flow velocity by vessel cross-sectional area, was similar in linear vessels and in individual vessels of a loop, averaging 8.6 ± 1.6 nl/min. Flow was always directed from the diaphragm periphery toward the medial tendineous region in linear vessels, whereas it was more complex and evidently controlled by intraluminal unidirectional valves in loops. The results suggest that loops might be the preferential site of lymph formation, whereas linear vessels would be mainly involved in the progression of newly formed lymph toward deeper collecting diaphragmatic ducts. Within the same hierarchic order of diaphragmatic lymphatic vessels, the spatial organization and geometrical arrangement of the submesothelial lacunae seem to be finalized at exploiting the alternate contraction/relaxation phases of diaphragmatic muscle fibers to optimize fluid removal from serosal cavities.

initial lymphatic vessel; extrinsic lymphatic mechanisms; diaphragmatic lymph flow