0041-1337/02/7302-178/0 TRANSPLANTATION Vol. 73, 178–185, No. 2, January 27, 2002 Copyright © 2002 by Lippincott Williams & Wilkins, Inc. Printed in U.S.A. Transplantation  ARTICLES POTENTIATING THE BENEFIT OF VASCULAR-SUPPLIED GLUTAMINE DURING SMALL BOWEL STORAGE IMPORTANCE OF BUFFERING AGENT 1 DAVID W. OLSON, 2 YASUHIRO FUJIMOTO, 2 KAREN L. MADSEN, 3 BRIAN G. STEWART, 2 MICHELLE CARLE, 2 JANICE ZENG, 4 LAURENCE JEWELL, 4 JENNIFER L. SHEASGREEN, 2 FENG T. CHONG, 2 NORMAN M. KNETEMAN, 5 DAVID L. BIGAM, 5 AND THOMAS A. CHURCHILL 2,6 Surgical-Medical Research Institute, and Department of Medicine, Division of Gastroenterology, University of Alberta, Edmonton, Alberta, and Department of Laboratory Medicine and Pathology, Division of Anatomical Pathology, and Department of Surgery, Division of Transplantation, University of Alberta Hospital, Edmonton, Alberta, Canada Background. Glutamine (gln)-supplemented Univer- sity of Wisconsin (UW) solution improves overall small bowel (SB) preservation. Sustained gln metabolism in a system devoid of hepatic detoxification will neces- sarily result in the accumulation of pH active end products leading to nonphysiologic pH shifts. We hy- pothesized that simultaneous addition of N,N-bis[2- hydroxyethyl]-2-aminoethane sulfonic acid (BES), a known buffering agent, would potentiate the benefi- cial effect of gln supplementation by addressing the fundamental metabolic principle of pH homeostasis. Methods. Sprague-Dawley SB rats were adminis- tered a vascular flush with one of four solutions: UW; UW90 mM BES (UWB); UW2% gln (UWG); or UW2% gln90 mM BES (UWBG). Indices of energetics, bar- rier function, gln catabolism, and histology (light and electron microscopy) were assessed over a 10-hr cold storage time course. Results. Superior gln utilization in the UWBG group was indicated by elevated levels of key catabolites (glutamate, aspartate, glycine, ammonia). The addi- tion of BES and gln resulted in significantly higher levels of all energetic parameters (ATP, total adenyl- ates) at 10 hr compared with UW, UWB, and/or UWG. Barrier function was markedly improved after 10 hr storage in the UWBG group; mannitol permeability was 169 nmol/cm 2 /hr versus 572 and 445 nmol/cm 2 /hr (for UW and UWG, respectively). Histologic injury at 10 hr was 5.5, 7.5, and 8 (Park’s grade) for UWBG, UWG, and UW. Ultrastructural damage was markedly re- duced with UWBG, as assessed by grade of mitochon- dria damage. Conclusion. This study strongly supports that the beneficial effects of gln-enriched UW solution can be amplified when combined with an effective buffering agent such as BES. Currently, no one vascular solution has been accepted un- equivocally for the preservation of small bowel (SB) for trans- plantation (1, 2). Multiple studies have documented that a variety of solutions, including University of Wisconsin (UW), are incapable of preventing clinically acceptable degrees of morphologic injury beyond 6 –10 hr of cold storage (3, 4). In an attempt to address this, solutions formulated on satisfy- ing organ-specific preservation requirements have been stud- ied but remain problematic in their clinical application. This is due to the fact that most organs, including SB, are pro- cured using a common vascular perfusate, as part of a multi- viscera procedure. Hence, the confines of multi-viscera pro- curement forces those interested in improving SB preservation to investigate supplementation of common per- fusates without altering their effectiveness. One such alteration has been the enrichment of UW, the current gold standard, with glutamine (gln), the primary fuel source of the enterocyte (5–7). When provided in supraphysi- ologic concentrations (2– 4%), gln has been shown to improve the morphologic and functional integrity of SB throughout extended storage periods (8). Ultimately, gln addresses SB- specific preservation requirements while operating under the confines of a common vascular solution. The effectiveness of exogenous vascular-supplied gln has been clearly documented in both in vitro (9) and in vivo (10, 11) organ systems. Additionally, use of this naturally occur- ring amino acid has not been shown to have detrimental effects on other organs. However, the metabolic consequences have not been studied for potential detrimental effects on both cellular function and morphology. Accumulation of po- 1 This study was supported by a grant from the Canadian Insti- tutes for Health Research and Canadian Association of Gastroenter- ology (T.A.C. and D.L.B.) and a grant from the Edmonton Civic Employees Charitable Assistance Fund (D.L.B. and D.W.O.). 2 Surgical-Medical Research Institute, University of Alberta. 3 Department of Medicine, Division of Gastroenterology, Univer- sity of Alberta. 4 Department of Laboratory Medicine and Pathology, Division of Anatomical Pathology, University of Alberta Hospital. 5 Department of Surgery, Division of Transplantation, University of Alberta Hospital. 6 Address correspondence to: Dr. Thomas A. Churchill, Surgical- Medical Research Institute, 1074 Dentistry-Pharmacy Building, University of Alberta, Edmonton, Alberta, Canada T6G 2N8. E-mail: tachurch@ualberta.ca. 178