The effect of transmural pressure on pumping activity in isolated bovine lymphatic vessels.

Abstract

SUMMARY1. Isolated preparations of bovine mesenteric lymphatics containing about seven valved segments were cannulated and set up in a perfusion system so that, when the preparation was not contracting, the inflow and outflow pressures were exactly equal and there was no flow through the preparation.2. Transmural pressure was varied by raising or lowering the inflow and outflow pressures simultaneously by the same amount.3. The isolated vessels showed rhythmic spontaneous activity; it consisted of quick contractions which spread rapidly over the entire preparation, each followed by a rapid relaxation and a diastolic pause.4. With each contraction, the preparation decreased in both length and diameter and generated an outflow pressure which pumped fluid in the direction determined by the orientation of the values.5. Raising the transmural pressure in the preparation increased the output of the preparation; this was achieved by an increase in both the frequency and force of the individual contractions.6. It was concluded that bovine lymphatics could propel fluid by their intrinsic activity at a rate which was related to the degree of distension of their walls.

Independent and interactive effects of preload and afterload on the pump function of the isolated lymphangion

“…Our conclusion is consistent with previous studies (3,14,15) of rat mesenteric lymphatics, where calculated pump output was maintained over a pressure range from 1 to 5 cmH 2 O because increases in contraction FREQ counterbalanced decreases in SV; likewise, measurements of SV, EF, and/or flow from bovine and ovine lymphatics suggest that optimal EDP in those vessels is between 2 and 8 cmH 2 O (12,14,15,22,24,26,28,34). An upper end of 8 cmH 2 O is likely to correlate with the diminished pump capacity observed in human peripheral lymphatic vessels during chronic lymphedema (31).…”

“…First, this is one of only three studies to characterize the relationship between diastolic pressure and function for a single, isolated lymphangion. With the exception of two short reports in untranslated Russian journals (18,27), previous studies (3,12,14,15,26,28) used multiple chains of lymphangions where, due to intrinsic contractile behavior that could be synchronized or nonsynchronized, P in was controlled only for the first segment of the chain and P out only for the last segment. Hence, the results presented here provide insights into the effect of preload on the function of the fundamental pumping unit of the lymphatic system: the lymphangion.…”

“…Previous studies using isolated chains of series-coupled lymphatic segments from several species have provided evidence that lymphatic vessels are exquisitely sensitive to changes in filling pressure and accordingly modulate pump output using the Frank-Starling mechanism (13,15,26,28). Notably, two studies have made use of cardiac-style analyses to study lymphatic pump function.…”

Modulation of lymphatic muscle contractility by the neuropeptide substance P

“…These vascular effects of SP would collectively increase flow/ pressure in capillaries and post-capillary venules and lead to increases in transcapillary fluid flux. The resulting increases in interstitial fluid volume and interstitial fluid pressure would enhance lymph formation (42, 43) and stimulate lymphatic pump activity through the well-described relationship of lymphatic filling pressure on lymphatic pumping (11,34,51).…”

Aged Lymphatic Contractility: Recent Answers and New Questions

“…The transmural pressure/stretch-dependent modulation of lymphatic contractility is one of the principle regulatory mechanisms of lymphatic pumping that serves a goal to adapt lymphatic transport to the different lymphatic preloads. [5][6][7][8][9][10] The alterations in stretch-related regulatory mechanisms in 24-mo old segments indicate that both pacemaking and contractile machinery are involved in age-related changes of active lymph pump in rat TD. Lowered lymphatic tone in aged TD segments, together with decreased lymphatic contraction amplitude, may be considered an indicator of age-related weakening of muscle cells and their diminished ability to create enough force to maintain the level of tone and contractile force appropriate to the lymphatic preloads.…”