Meeting Abstract
24.2 Friday, Jan. 4 Form and function; identifying the underlying regulatory mechanisms of intestinal performance SECOR, S.M.*; COX, C.L.; LIGNOT, J.-H.*; Univ. of Alabama; Univ. of Alabama; CEPE-CNRS, Louis Pasteur Univ. ssecor@biology.as.ua.edu
Infrequently feeding snakes possess the adaptive capacity to widely regulate gastrointestinal performance with feeding and fasting. Feeding triggers a doubling of small intestinal mass and 3 to 10-fold increases in intestinal nutrient uptake rates and hydrolase activities. Upon the completion of digestion, the small intestine reduces its size and downregulates transporter and hydrolase activities. Cellular mechanisms that underlie the regulation of intestinal function could include changes to: (1) transporter and enzyme activities, (2) transporter and enzyme densities, and/or (3) luminal surface area. To explore the involvement of these regulatory mechanisms, we measured uptake rates of the amino acids L-leucine, L-proline, and D-glucose, activities of aminopeptidase-N (APN) and maltase, and cellular morphology from five regions of the small intestine of Burmese pythons fasted and at 9 time points after feeding (0.25�15 days). With feeding, pythons experienced a rapid increase (4-fold) in microvillus length and in luminal surface area that was correlated with postfeeding changes in nutrient uptake rates and hydrolase activities for the proximal small intestine. Lengthening of the microvilli apparently results from the trafficking of cytoplasmic stores of G-actin, cytoskeletal proteins, and membrane to the luminal surface. This morphological response is consistent throughout the small intestine and matches positional changes in amino acid uptake and APN activity. However it does not match the strong proximal to distal decline in maltase activity and glucose uptake. For the python, modulating luminal surface area explains much of the postfeeding changes in intestinal protein digestion and amino acid absorption; however this mechanism appears to be coupled to other mechanisms in the regulation of simple sugar digestion and absorption.
