Current topics of physiology and pharmacology in the lymphatic system

We have reviewed physiological significance of rhythmical spontaneous contractions of collecting lymph vessels. which play a pivotal role in lymph transport and seem to control lymph formation through changing the pacemaker sites of the rhythmic contractions and contractile patterns of the lymphangions. A characteristic feature that the rhythmic pump activity works in vivo physiologically under the specific environment of lower oxygen tension in lymph (25-40 mm Hg) has been evaluated. With the characteristic feature. generation of endogenous nitric oxide (NO) from lymphatic endothelial cells and/or activation of ATP-sensitive potassium channels (K-ATP) are reviewed to play crucial roles in the regulation of lymph transport at physiological or pathophysiological conditions. Chemical substances released front malignant tumor cells and tumor-derived parathyroid hormone-related peptide (PTHr-P) are also shown to cause a significant reduction of lymphatic pump activity through generation of endogenous NO and activation of K-ATP channels. Finally. we have discussed physiological significance and roles of the lower oxygen tension in lymph. generation of endogenous NO. and activation of K-ATP in lymph formation. lymph transport, and the functions of lymph nodes. (C) 2004 Elsevier Inc. All rights reserved.