Age Difference in the Intestinal Phosphomonoesterase Activity of Mice ∗

Abstract

The intestinal mucosal cells have been shown to contain specific phosphatases along with a group of nonspecific phosphomonoesterases. Ockerman (1) has shown the presence of a glucose 6-phosphatase in the microsomal fraction of the jejunal mucosal cells. A Na⁺, K⁺, activated adenosine triphosphatase activity has been shown to reside in the cell membrane fraction (2, 3). Whereas the adenosine triphosphatase has been implicated in the action of the intestinal sugar pump (4), the metabolic function of glucose-6-phosphatase awaits elucidation. While the precise roles of the intestinal phosphatases remain unknown, their involvement in the processes of mucosal transport and metabolism is a good possibility.

The present report is concerned with changes in the intestinal phosphomonoesterase activity in relation to the age of the animal. This study was undertaken in view of the possibility that the process of aging may have an influence on the behavior of the enzyme apparatus which in turn may suggest changes in the intestinal metabolic and absorptive functions.

Materials and Methods. The homogenate and the cell membrane fraction used in this study as the sources of enzyme were prepared from two groups of female mice of B6D2F₁/J strain (The Jackson Laboratory, Bar Harbor, Maine). One of these, consisting of 11-month-old mice weighing 34.0 + 2.0 g, is referred to in this paper as the adult group. The other group was comprised of 34-month-old animals weighing 26 + 1.5 g and is referred to as the aged group. 1

The animals were sacrificed after a 24-hr fast. The entire small intestine was removed, everted, and scraped on a chilled glass surface by means of a glass slide. Two-tenths percent (w/v) homogenates of mucosal scraping were prepared, in a diluent of one part Krebs-Ringer-bicarbonate and three parts tris (hydroxymethyl) aminomethane-HCl (Tris) buffer adjusted to pH 8.00. The homogenate was centrifuged at 1000g for 40 min, and the resulting sediment was suspended in the Krebs-Ringer-bicarbonate and Tris mixture to a final volume equal to that of the homogenate used in obtaining that amount of sediment.