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RATE‐SENSITIVE CONTRACTILE RESPONSES OF RAT MESENTERIC LYMPHATICS TO CIRCUMFERENTIAL STRETCH
Author(s) -
Lane Megan,
Davis Ann M.,
Gashev Anatoliy,
Zawieja David C.,
Davis Michael J.
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a485-c
Subject(s) - preload , contraction (grammar) , anatomy , lymphatic system , chemistry , muscle contraction , medicine , cardiology , hemodynamics , biology , pathology
Both the amplitude (AMP) and frequency (FREQ) of phasic contractile activity in rat portal vein are more sensitive to the rate of length change than to the absolute length (Circ Res 36 :, 1975). Because lymphatics exhibit similar phasic activity, we hypothesized that lymphatic muscle would exhibit rate‐sensitive responses to stretch. Rat mesenteric lymphatics (~100 um, ID) were studied in vitro using customized wire‐ and pressure‐ myographs that allowed servo‐control of diastolic force, diameter, or pressure (preload). While recording spontaneous activity, preload was increased at variable rates, using preload ramps with different slopes, from the lowest value at which spontaneous activity occurred to the optimal level. Both contraction AMP and FREQ increased with preload, as reported previously. Superimposed upon this were bursts of contractions during the rising preload phase. The ratio of contraction FREQ (ramp/end) was always greater than 1 and increased with rate. In contrast, the AMP ratio was always less than 1 and was independent of rate. Off‐responses (contraction inhibition) were typically more pronounced than on‐responses. These results suggest that lymphatic vessels are sensitive to the rate of change of preload in a different way than portal vein. One explanation is that the electrical pacemaker in the lymphatic wall is rate‐sensitive but the muscle itself is not. Supported by NIH HL‐75199.