INFLUENCE OF ANESTHETIC REGIMENS ON INTESTINAL-ABSORPTION IN RATS

We compared the influence of anesthetic regimens using urethane (U), pentobarbital (P), ether (E), and ketamine/midazolam (K) on the intestinal absorption of several probes using a single-pass perfusion technique in rats. The selected probes were D-glucose (1 mM) for the resistance of the unstirred water layer (UWL), D-glucose (100 mM) for the capacity of carrier-mediated D-glucose transport, L-glucose, and urea for membrane-limited passive transport, and , tritiated water ((H2O)-H-3) for blood flow at the absorption site. The absorbed fraction Of D-glucose (1 mM) was the smallest for U and the largest for P, suggesting that the resistance of UWL is the largest for U and the smallest for P. The absorbed fraction of D-glucose (100 mM) was the largest for P (U = E = K < P), suggesting a higher capacity of carrier-mediated D-glucose transport for P. The absorbed fraction of urea was similar for all anesthetics, while that of L-glucose was the smallest for K (U = P = E > K). Although the results for these two markers of membrane-limited passive transport were inconsistent, the passive permeability of the intestinal membrane may be lower when treating with K. The intestinal absorptions Of D-glucose (1 and 100 mM), L-glucose, and urea were, in general, lower with any of the anesthetics than under nonanesthesia (N), suggesting increased resistance of UWL and decreased intestinal membrane permeability by carrier-mediated and passive transport under anesthesia. The only exception was the absorption Of D-glucose (100 mM) under P, which was comparable to that under N. The results were similar when considering the membrane permeability clearance estimated by correcting for the resistance of UWL. The blood flow at the absorption site, estimated from the absorption of (H2O)-H-3, was decreased under U, compared with N, and increased under K (U < P = E = N < K). The information obtained in this study is useful for the comprehensive interpretation of intestinal absorption data obtained under different anesthetic regimens and the prediction of intestinal absorption in vivo.