American Jolxnal of Physiology

HAKIM, A. A., AKD NATHAN LIFSON. Effects of pressure on water and solute transport by do,g intestinal mucosa in vitro. Am. J Physiol. 216(Z) : 276-284. 1969.-This paper describes in some detail of canine intestinal mucosa ( 11, 12). The physiological relevance of the preparation is favored by its transport behavior, including dependence of water transport from isotonic Ringer fluid on the presence of glucose in the medium, water absorption against an osmotic activity difference, uphill glucose movement, and chloride the relationship between hydrostatic pressure and fluid transport found for the clog intestinal mucosa in vitro. With glucosecontaining Krebs-bicarbonate-Ringer solution as the bathing fluids, the rate of fluid absorption was not affected by excess mucosal pressures up to 20 cm HYO. By contrast, excess serosal pressures of about 4 cm Hz0 reduced fluid transport to zero and higher serosal pressures reversed absorption to secretion. Excess serosal pressure very probably increases the hydraulic permeability coefficient by widening existing, or opening new channels. The kinetics of solute transport during the secretory flow is consistent with this view. Consideration is given to the possible relevance of the asymmetry of the pressure sensitivity to in vivo intestinal function. Misconceptions concerning the interpretation of unidirectional fluxes of water during intestinal absorption or secretion are discussed.