Optimizing the concentration of hydroxyethylstarch in a novel intestinal-specific preservation solution q Matthew S. Kokotilo a , Jodi Carter b , Aducio Thiesen b , Ming H. Chen a , Angela Ochs a , Rachel G. Khadaroo a , Thomas A. Churchill a,⇑ a Department of Surgery, University of Alberta, Edmonton, Alberta, Canada T6G 2B7 b Department of Laboratory Medicine and Pathology, University of Alberta, Canada article info Article history: Received 6 May 2010 Accepted 12 August 2010 Available online 19 August 2010 Keywords: Intraluminal preservation solution Intestinal-specific Oncotic/osmotic agents Organ preservation Energetic stress Oxidative stress Osmotic stress abstract Introduction: Our lab has developed an effective nutrient-rich solution that facilitates energy production and control of oxidative stress during static cold storage of the intestine; however, the requirement for oncotic agents, such as hydroxyethylstarch (HES), has not been evaluated. This study investigated the effectiveness and requirement for HES in an intraluminal preservation solution during a clinically rele- vant period of cold storage. Methods: Rat intestines were procured, including an intravascular flush with University of Wisconsin solution followed by a ‘back table’ intraluminal flush with a nutrient-rich preservation solution contain- ing varying amounts of HES (n = 6 per group): Group 1, 0%; Group 2, 2.5%; Group 3, 5%; Group 4, 10%. Energetics, oxidative stress, and morphology were assessed over a 24 h time-course of cold storage. Results: Overall, the 5% HES solution, Group 3, demonstrated superior energetic status (ATP and total ade- nylates) compared to all groups, P < 0.05. Malondialdehyde levels indicated a reduction in oxidative stress in Groups 3 and 4 (P < 0.05). After 12 h, median modified Parks’ grades for Groups 2 and 3 were signifi- cantly lower than Groups 1 and 4, P < 0.05. Conclusion: Our data suggests that when employing an intraluminal preservation solution for static organ storage, oncotic support is a fundamental requirement; 5% HES is optimal. Ó 2010 Elsevier Inc. All rights reserved. Introduction During the last several years, our laboratory has developed an amino acid (AA)-based preservation solution tailored to the meta- bolic requirements of the small bowel. Numerous in vitro and in vivo studies have demonstrated that luminal administration of this solution results in improved morphology and metabolic status of the small bowel following cold storage, ischemia–reperfusion, and experimental transplantation [26,9,22,27,28]. Although the composition and route of administration differ between our solu- tion and the UW solution, there exists a major commonality: the presence of osmotic impermeants to prevent tissue edema. At a molecular level, under normal circumstances, Na+/K+ ATPase en- sures Na+ extrusion from the cell, which results in Na+ functioning as an osmotic agent outside the cell [2]. The extracellular Na+ counteracts the osmotic pressure developed from intracellular pro- teins and impermeant anions. However, the situation is much dif- ferent during organ storage. Hypothermia and declining ATP levels collectively suppress Na+/K+ pump activity, causing Na+ and Cl to follow concentration and electrochemical gradients into the cell. As these ions enter, water follows and the cell swells. To offset the flow of water into the cell, an impermeant agent is required extra- cellularly; 110–140 mmol/l has been established as the effective concentration range for an intravascular solution [2]. Hydroxyethylstarch (HES), a modified natural polymer of amy- lopectin [36], is the colloid contained in UW solution for oncotic support [32]. Although the solution contains HES on the basis of preventing cold storage interstitial edema [32], there exists some controversy over its effectiveness, especially for static organ stor- age. Some studies report that HES may be omitted from the UW solution without detrimental effects on organ preservation [38,14,4], while others indicate a protective role of HES on stored tissues [2,32,1,6,7,20]. Since these studies deal solely with the intravascular delivery of preservation solution, they do not provide information about the role of colloids in solutions administered intraluminally for intestinal grafts. Although our AA solution con- tains low molecular weight osmotic agents, we suspect that an 0011-2240/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.cryobiol.2010.08.001 q Statement of funding: This research was supported by operating funds awarded by the Canadian Institutes of Health Research (CIHR) to TA Churchill and salary award from Alberta Heritage Foundation for Medical Research (AHFMR) to MS Kokotilo. ⇑ Corresponding author. Address: 2D2.28 Walter Mackenzie Center, Department of Surgery, University of Alberta, Edmonton, Alberta, Canada T6G 2B7. Fax: +1 780 407 7394. E-mail address: tachurch@ualberta.ca (T.A. Churchill). Cryobiology 61 (2010) 236–242 Contents lists available at ScienceDirect Cryobiology journal homepage: www.elsevier.com/locate/ycryo