Phase and tonic contractions of lymphatic vessels and nodes under the action of atrial natriuretic peptide

Abstract

Introduction and purpose. Active lymph flow ensured by the phase contraction of lymphatic vessels and nodes is regulated by humoral mechanisms. The role of atrial natriuretic peptide (ANP) in the modulation of lymph flow has been poorly studied. The goal of the study was to examine the effect of the ANP, which is released into the blood by increasing the volume of circulating blood, on the active transport function of lymphatic vessels and nodes. Materials and methods. The study was performed on isolated segments of bovine mesenteric lymphatic vessels with a diameter of 1.5-2.0 mm (n = 47) and the capsule strip lymph nodes (n = 42). The contractive function of lymphatic vessels and nodes was examined using the equipment for the study of isolated preparations with FORT-10 transducer. The data were processed in program Labmaster. Results and discussion. ANP (1-100 ng/ml) caused a dose-dependent decrease in frequency and amplitude of spontaneous contractions and tone of lymphatic vessels and nodes. The ANP-induced relaxation of lymphatic vessels and nodes was not modified by pretreatment with 5x10 -5 M L-NAME, 3x10 -6 M diclofenac sodium and 1x10 -5 M methylene blue. The relaxation, however, was significantly reduced by pretreatment with 1x10 -5 M glibenclamide. The mechanical removal of endothelial cells in the lymph vessels and nodes caused no significant effect on the ANP-induced relaxation. Conclusions. The results of the study show that ANP inhibits the transport of lymph by reducing the amplitude and frequency of the phase contractions and relaxation of smooth muscle of lymphatic vessels and nodes. The effect of ANP is endothelium-independent and is mediated by activation of plasmalemmal ATP-sensitive K + channels of smooth muscle cells.