Lymphatic pump-conduit duality: contraction of postnodal lymphatic vessels inhibits passive flow

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 296; no. 3; pp. H662 - H668
• Main Authors: Quick, Christopher M, Ngo, Bruce L, Venugopal, Arun M, Stewart, Randolph H
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.03.2009
• Subjects: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid - pharmacology; Animals; Calcium - metabolism; Cardiovascular system; Cattle; In Vitro Techniques; Lymph - physiology; Lymphatic system; Lymphatic Vessels - drug effects; Lymphatic Vessels - physiology; Mathematical models; Mesentery; Muscle Contraction - drug effects; Muscle Relaxation; Muscle, Smooth - physiology; Pressure; Time Factors; Veins & arteries
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.00322.2008

Michael E. DeBakey Institute Texas A&M University, College Station, Texas Submitted 27 March 2008 ; accepted in final form 29 December 2008 Lymphangions, the segments of lymphatic vessels between valves, exhibit structural characteristics in common with both ventricles and arteries. Although once viewed as passive conduits like arteries, it has become well established that lymphangions can actively pump lymph against an axial pressure gradient from low-pressure tissues to the great veins of the neck. A recently reported mathematical model, based on fundamental principles, predicted that lymphangions can transition from pump to conduit behavior when outlet pressure falls below inlet pressure. In this case, the axial pressure gradient becomes the major source of energy for the propulsion of lymph, despite the presence of cyclical contraction. In fact, flow is augmented when cyclical contractions are abolished. We therefore used an in vitro preparation to confirm these findings and to test the hypothesis that lymphangion contraction inhibits flow when outlet pressure falls below inlet pressure. Bovine postnodal mesenteric lymphatic vessels harvested from an abattoir were subjected to an inlet pressure of 5.0 cmH 2 O and an outlet pressure that decreased from 6.5 to 3.5 cmH 2 O under control conditions, stimulated with U-46619 (a thromboxane analog) and relaxed with calcium-free solution. Under control conditions, lymphatic flow markedly increased as outlet pressure fell below inlet pressure. In this case, the slopes of the flow versus axial pressure gradient increased with calcium-free conditions (61%, n = 8, P = 0.016) and decreased with U-46619 stimulation (21%, n = 5, P = 0.033). Our findings indicate that the stimulation of lymphatic contractility does indeed inhibit lymphatic flow when vessels act like conduits. lymphangion conductance; contractility Address for reprint requests and other correspondence: C. M. Quick, Michael E. DeBakey Inst., Texas A&M Univ., TAMU 4466, College Station, Texas 77843-4466 (e-mail: cquick{at}tamu.edu )