Electrolyte Transport Across the Mouse Small Intestine

Abstract

Reports from this laboratory (1, 2) and others (3)(4)(5)(6)(7) have demonstrated that the mammalian intestine provides a useful experimental model for studies on the transport mechanisms for electrolytes and nonelectrolytes. The animals used in these studies were mainly rats, rabbits, hamsters, and guinea pigs. The use of mouse intestine as a model system for such studies has not been previously explored.It is generally agreed that the measured ion fluxes and short-circuit current across the mammalian intestine vary greatly with the thickness of the intestine, presumably because of the presence of several layers in addition to the mucosal membrane. Therefore, data obtained with stripped intestinal mucosal membrane is preferable to that obtained with an intact intestine (4, 6 , 7). Since mouse intestine is much thinner than that of mammals previously studied, one wonders would the ion fluxes across the thin intact mouse intestine correspond closely to those observed in the stripped mammalian intestinal mucosa. If so, the mouse intestine could provide a useful and simple tool in future studies on drug effects on intestinal transport systems.Methods. Albino S wiss-Webster mice, weighing an average of 30-40 g were used. They were kept in a constant-temperature room with food and water ad lib. for 7 days or longer after purchase. The mice were killed by decapitation, and the ab-. 3To whom reprint requests should be sent.domen was opened. A section of jejunumileum was removed and opened along the line of mesenteric attachment, rinsed with Ringer solution and mounted in a lucite Ussing chamber having an aperture area of 1.3 cm2. Mammalian Ringer or other isotonic solution was used as bathing fluid. Seven milliliters of bathing solution was pipetted into each of the two chambers separated by the intestinal membrane. The bathing solution was continuously stirred and oxygenated by bubbling with 95% 0,-5% CO, gas. The chamber was kept in a 37°C incubator throughout the experiment. The composition of each bathivg solution is given in Table I. Calomel electrodes were placed close to each side of the membrane for potential difference (PD) measurement. Current was sent through two PbS04 electrodes to zero out the PD and recorded in an Esterline-Angus recorder. The design of the Ussing chamber and the details of the electrical measurements have been described previously (8, 9). Radioactive 22Na and 36Cl were used to measure the sodium and chloride fluxes across the short-circuited intestine. Bathing solutions from both sides were sampled at half-hour intervals and were counted in duplicate in automatic well-scintillation and liquid scintillation counters. Standard 22Na and 36Cl were counted simultaneously with the samples. The ratios of counting of these standard solutions by the two counters were then used to determine the amount of 22Na and 3sCl in the collected samples. Electrolyte fluxes and short-circuit current (Zsc) are expressed in microequivalents (pEq) per square centimeter per hour.Results. Electrical properties of mo...

Stem Cells and the Niche: A Dynamic Duo

“…However, recent lineage-tracing analysis and in vitro culturing techniques provided convincing evidence that crypt base columnar cells (CBCs) that express leucine-rich repeat-containing G protein-coupled receptor 5 (Lgr5) behave as stem cells in intestinal crypts (Barker et al, 2007; Sato et al, 2009). In the murine small intestine, CBCs are intercalated between Paneth cells and are in direct contact with a basement membrane at the base of the intestinal crypt (Chang et al, 1974). …”