Short‐Term Functional Adaptation of Bovine Mesenteric Lymphatic Vessels to Partial Occlusion

In‐vitro studies have shown that contractile status of lymphatic vessels is altered by acute changes in transmural pressure (P) and luminal flow (Q); however, their responses to prolonged changes are unknown. We hypothesized that lymphatic vessels adapt to prolonged changes in P and Q. Bovine mesenteric lymphatic vessels were partially occluded in vivo for 3 days. On day 3, segments ~3 mm in diameter from occluded vessels – upstream (UP) and downstream (DN) from the occlusion ‐ and non‐occluded vessels (CG) were cannulated in isolated baths. Spontaneous contractions were recorded at different pressures (1, 3, 6, 9, and 12 cmH 2 O) under high shear (50 μPa) and low shear (8.1 μPa). An index of conduit behavior of the occluded vessels (UP, 0.92 ± 0.01 and DN, 0.91 ± 0.01) was larger than that of CG (0.87 ± 0.01). The contraction frequency (F) and normalized stroke volume were both higher in CG (5.44 ± 0.70 min −1 , 0.31 ± 0.03) than in UP (3.85 ± 0.84 min −1 , 0.22 ± 0.03) and DN (3.82 ± 0.84 min −1 , 0.19 ± 0.03). Normalized diastolic volume and calculated flow (SV x F) were both larger in UP (0.78 ± 0.05, 4.73 ± 0.79 mm 2 .min −1 ) than in DN (0.69 ± 0.05, 3.05 ± 0.79 mm 2 .min −1 ). We conclude that lymphatic vessels respond to 3 days of decreased flow by decreasing resistance and to 3 days of elevated transmural pressure by increasing diastolic diameter and contractility. This project was funded by NIH grant R01 HL092916.