THE VALUE OF INVIVO ELECTROPHYSIOLOGICAL MEASUREMENTS FOR MONITORING FUNCTIONAL ADAPTATION AFTER MASSIVE SMALL-BOWEL RESECTION IN THE RAT

The process of functional adaptation after extensive small bowel resec tion is complex and imprecisely understood. In vivo electrophysiologic al measurements for monitoring the functional adaptive process after m assive small bowel resection in Brown-Norway rats were evaluated. Rats underwent either a sham operation (SH) or a 90% small bowel resection (SB). Standard rat chow was fed in unlimited quantities. At three or 10 weeks after operation, jejunal and ileal transepithelial potential differences (PD, mV) were determined. Electrogenic ion transport in th e villus was measured after glucose (sodium coupled active glucose abs orption; PD-glu) and in the crypt, after theophylline infusion (theoph ylline stimulated chloride secretion; PD-theo). Biopsies were taken si multaneously. Each experimental group consisted of three to five anima ls. At three weeks the PD-theo and PD-glu in SB rats were significantl y lower than in SH rats in both jejunal and ileal segments. At 10 week s PD-theo and PD-glu were significantly diminished in the jejunal segm ent of the SB rats compared with the SH rats. The values of PD-theo an d PD-glu in the ileal segments were, however, no longer different betw een the two groups. Three and 10 weeks after operation the length of t he villi in the SB group was increased significantly compared with the SH controls. These results indicate that in the early phase of adapta tion in vivo electrophysiological variables do not correlate with hist ological changes in the SB rats. This might be due to cell immaturity resulting from an increased rate of cell turnover or lack of intercell ular tight junctions. This hypothesis is supported by a recovery of PD responses in the ileum 10 weeks after resection.