Objective: To measure lymphocyte velocity, lymphatic contraction, and shear stress in phasically contracting lymphatics in situ.
Methods: A high-speed video system was used to capture multiple contraction cycles in rat mesenteric lymphatic preparations. The images were analyzed to determine fluid velocity, volume flow rate, wall shear stress, and retrograde flow.
Results: Lymphocyte density and flux varied from 326 to 35,500 cells/μ L and 206 to 2030 cells/min, respectively. Lymphatics contracted phasically, with a mean diameter 91 ± 9.0 μ m and amplitudes of 39%. Lymph velocity varied with the phasic contractions in both direction and magnitude with an average of 0.87 ± 0.18 and peaks of 2.2–9.0 mm/s. The velocity was ∼ 180° out of phase with the contraction cycle. The average lymph flow was 13.95 ± 5.27 μ L/h with transient periods of flow reversal. This resulted in an average shear of 0.64 ± 0.14 with peaks of 4–12 dynes/cm2.
Conclusions: High-speed lymphocyte tracking provided the spatial and temporal resolution to measure lymphocyte flux throughout the phasic contraction. Poiseuille flow was a reasonable model for estimating wall shear stress through most of the phasic contraction cycle of the intervalvular lymphatic segments. Shear rate was low but had large variations in magnitude compared to that seen in blood vessels.