AJP - Gastrointestinal and Liver Physiology, Vol 261, Issue 3 433-G442, Copyright © 1991 by American Physiological Society

ARTICLES

Comparison of fluid absorption by bovine and ovine descending colon in vitro

A. T. McKie, I. A. Goecke and R. J. Naftalin
Division of Biomedical Sciences (Physiology Group), King's College London, Strand, United Kingdom.

Although bovine and ovine descending colon absorbed solute and sodium at approximately the same rate in vitro, water absorption by bovine colon was faster (15.0 +/- 2.0 microliters.h-1.cm-2, n = 8) than by ovine colon (8.6 +/- 1.3 microliters.h-1.cm-2, n = 9; P less than 0.01). Consequently, the observed osmolality of cattle absorbate was lower (364 +/- 13 mosmol/kg, n = 8) than with sheep (807 +/- 135 mosmol/kg, n = 9; P less than 0.01). Paracellular permselectivity was examined to elucidate this difference; the permeability of bovine descending colon to [3H]polyethylene glycol 400 and 4000 was higher than in sheep (P less than 0.001). A paracellular solvent drag was observed in bovine but not in ovine colon, and the electrical resistance of bovine colon was lower (16.0 +/- 1.4 omega.cm2) than ovine colon (28.0 +/- 2.4 omega.cm2; P less than 0.001). Pore radii of 2.5 nm for ovine and 5 nm for bovine colonic paracellular route were estimated from these data. It is concluded that an increased hydraulic conductance of the "active" route for solute absorption combined with raised solute reflux via the wider paracellular pathway may account for the failure of cattle to form a hypertonic absorbate and, consequently, hard feces.

This article has been cited by other articles:

				A T McKie, P S Zammit, and R J Naftalin Comparison of cattle and sheep colonic permeabilities to horseradish peroxidase and hamster scrapie prion protein in vitro Gut, December 1, 1999; 45(6): 879 - 888. [Abstract] [Full Text] [PDF]