AJP - Gastrointestinal and Liver Physiology, Vol 246, Issue 5 587-G593, Copyright © 1984 by American Physiological Society
Comparison of colonic and ileal propulsive capabilities under conditions requiring hydrostatic work
W. A. Weems and N. W. Weisbrodt
The intrinsic ability of cat colonic segments to do hydrostatic work to
expel fluid was investigated in vitro and compared with the propulsive
ability of ileal segments evaluated under identical conditions. Colonic
segments spontaneously produced propulsive complexes at an average interval
of 4.8 min when basal intraluminal pressure was set at 5 cmH2O. These
complexes produced a net ejection of fluid in the aboral direction. When
the capacitance of the evaluation system was set at 0.025 ml/cmH2O, colonic
segments ejected only 5% of their content. This percentage increased to 23%
when evaluation capacitance was increased to 0.125 ml/cmH2O. Peak aboral
pressure associated with these complexes was approximately 37 cmH2O at both
capacitances. Ileal segments aborally ejected almost twice as much fluid
(44% of their luminal content) as did colonic segments at a capacitance of
0.025 ml/cmH2O even though ileal luminal content was five times less than
colonic content. The aborally ejected volume per complex did not change
when ileal segments were evaluated at two different capacitances even
though higher pressures were required to eject fluid at the lower
capacitance than at the higher capacitance. These results indicate that the
propulsive behavior of ileal and colonic segments has some qualitative
aspects that are similar but that only the propulsive ability of colonic
segments is pressure limited under the conditions tested. Possible
mechanisms that might produce this limitation are considered.
