LYMPH PUMP MECHANICS IN THE RABBIT HIND LEG

The mechanisms that govern fluid uptake by the initial lymphatics and adjustment of lymph flow rates remain to a large degree uncertain. The aim of this study was to examine how passive tissue movement contribu tes to lymph flow rates, Lymph fluid was collected via a cannula inser ted into one of the popliteal prenodal lymphatics in the rabbit hind l eg. Lymph flow rates were measured during periodic whole leg rotation and controlled oscillatory massage of the dorsal skin of the foot. Wit hout whole leg rotation, lymph flow remained at low values (<0.01 ml/h ). Introduction of whole leg passive rotation caused a frequency-depen dent increase in lymph flow rates, which were increased linearly with the log of frequency between 0.03 and 1.0 Hz. Local skin massage in th e region of the initial lymphatics also led to a similar increase of l ymph flow rates dependent on frequency as well as amplitude of skin di splacement. Lymph flow rates during local skin massage reached a compa rable order of magnitude regardless of whether the animal was alive or the heart had been arrested, suggesting that local lymph flow rates c an be adjusted by periodic tissue motion independently of capillary fl uid filtration pressures. The results indicate that periodic expansion and compression of initial lymphatics provide a mechanism for lymph p umping.