FLUID PRESSURES IN THE RABBIT POPLITEAL AFFERENT LYMPHATICS DURING PASSIVE TISSUE MOTION

Abstract

The mechanisms of pressure and flow generation in the initial lymphatic network remainundefined in many details. Active pump mechanisms by lymph smooth muscle contraction havebeen demonstrated in collecting lymph ducts while passive mechanisms by periodic lymphcompression in noncontractile initial lymphatics have received relative little attention. The aimof this study was to examine lymph flow before and during periodic passive tissue deformationunder different lymph outflow pressures. Lymph flow rate and lymph outflow pressure weremeasured in rabbit popliteal prenodal lymphatics during whole leg rotations. The hind legs wererotated in a sagittal plane at selected frequencies. During constant leg rotation, lymph flow ratesreached steady levels which depend on lymph outflow pressure. When lymph outflow wasoccluded, intralymphatic pressures increased progressively to levels which depend on legrotation frequency. Both lymph flow rate and pressure showed higher values with foot edemathan in the absence of foot edema. These results suggest that periodic tissue deformation, lymphoutflow pressure, and interstitial free fluid volume are important determinants of the lymph flowrate.