Meeting Abstract

P2.90  Thursday, Jan. 5  Compensatory changes in assimilation capability in response to low protein diets in mice (Mus musculus) DERRICKSON, E.M.*; COOK, M.; Loyola University Maryland; Loyola University Maryland

The protein content of food directly impacts the growth and development of animals. Because low protein diets likely are encountered by omnivorous and herbivorous mammals, mice may have evolved adaptations that allow them to compensate for low protein, and thus moderate the impact of diet on fitness. We hypothesized that lactating mice on a low protein diet would demonstrate morphological and physiological changes in foregut compartments (stomach, small intestine) consistent with increased assimilation efficiency, and no changes in hindgut organs (cecum, colon). Mice were maintained on isocaloric diets containing low or optimal protein (10 or 20% respectively) during gestation and lactation, and sacrificed at 15-17 days of lactation. Wet and dry mass of organs and organ contents were obtained, and samples of small intestine were removed for enzyme assay and for fixation. Stomach wet mass and small intestine wet and dry mass each increased in mice on the low protein diet. No difference was seen in wet or dry mass of food in any compartment. Aminopeptidase activity/g tissue in the proximal, mid and distal regions of the small intestine did not differ between diet treatments. Small intestine diameter (but not length) was greater in mice on the low protein diet. These changes suggest that mice improve assimilation by increasing gastric secretion and increasing intestinal surface area for absorption of amino acids. We have no evidence that mice retain food preferentially in the foregut or increase aminopeptidase activity at the cellular level. We are measuring villus and crypt diameter along the intestine to determine what changes at the microscopic level account for the increased mass and diameter of the small intestine.