Intestinal Mitochondrial Dysfunction in Surgical Stress 1 Anup Ramachandran, M.Sc., Susama Patra, M.D., and K. A. Balasubramanian, Ph.D. 2 Department of Gastrointestinal Sciences, The Wellcome Trust Research Laboratory, Christian Medical College & Hospital, Vellore 632004, India Submitted for publication August 24, 2000; published online May 7, 2001 Background. Surgical stress is associated with al- tered intestinal function. Our earlier study using a rat model indicated that oxidative stress plays an impor- tant role in this process. Since mitochondria are cru- cial to cellular function and survival and are both a target as well as a source of reactive oxygen species, the present study looks at the changes in enterocyte mitochondria during surgical stress. Methods. Surgical stress was induced by opening the abdominal wall and handling the intestine as done dur- ing laparotomy. Mitochondria were prepared from the isolated enterocytes at different time periods after sur- gical stress. The effect of surgical stress on enterocyte mitochondrial ultrastructure, respiration, anti-oxidant enzyme activity, thiol redox status, calcium flux, perme- ability, and matrix enzymes was then studied. Results. Surgical stress resulted in alterations in mito- chondrial respiration and thiol redox status. It was also associated with altered mitochondrial matrix enzyme activity, decreased superoxide dismutase activity, in- duction of mitochondrial permeability transition, and swelling, as well as impairment of mitochondrial cal- cium flux. These alterations were seen at a maximum of 60 min following surgical stress and were reversed by 24 h. Conclusions. Laparotomy and mild intestinal handling itself results in enterocyte mitochondrial damage. Since mitochondria are important cellular organelles, this damage can probably lead to compromised intestinal function. © 2001 Academic Press Key Words: surgical stress; intestine; mitochondria. INTRODUCTION The intestine functions as an effective barrier to enteric bacteria under physiologic conditions, prevent- ing their translocation to the systemic circulation. The gut is sensitive to surgical stress even if the surgical procedure is done at a remote location, and studies have shown that bilateral lower extremity ischemia/ reperfusion results in increased intestinal permeabil- ity [1]. Surgical stress results in neuroendocrine re- sponses [2], which can affect hepatic circulation. Hepatic mitochondrial redox status is altered due to tissue hypoxia in surgical stress, leading to shortage of energy substrates and an energy crisis [3]. The mito- chondria are extensively studied organelles due to their central role in cellular energy production, and this organelle also plays an important role in calcium homeostasis [4]. Due to these important functions, any damage to mitochondria can have grave consequences for cellular function. Mitochondria are sensitive to a wide variety of insults, but among them oxidative stress is important since mitochondria consume about 90% of the oxygen utilized by the cell and are an important source of cellular oxygen free radicals [5]. Most of the studies on surgical stress deal with change occurring at the tissue level, and details of cellular damage during this process are scant. Our earlier ob- servations have indicated that oxidative stress in en- terocytes might be responsible for altered intestinal permeability seen during surgical stress induced by laparotomy with bowel manipulation [6]. It is probable that these changes at the functional level are due to damage to intestinal mitochondria, which play a num- ber of important cellular roles. In order to understand changes occurring at the subcellular level in the intes- tine during surgical stress, this study has looked at various mitochondrial functions in the enterocyte after inducing surgical stress by laparotomy and bowel ma- nipulation in the rat. 1 This study was supported by the Wellcome Trust, London, and the Council of Scientific and Industrial Research, Government of India. A.R. is a Senior Research fellow of the Council of Scientific and Industrial Research. 2 To whom correspondence and reprint requests should be addressed at Wellcome Trust Research Laboratory, Department of Gastrointesti- nal Sciences, Christian Medical College Hospital, Vellore 632004, India. Fax: 91-0416-232035. E-mail: wubalu@hotmail.com. Journal of Surgical Research 99, 120 –128 (2001) doi:10.1006/jsre.2001.6104, available online at http://www.idealibrary.com on 120 0022-4804/01 $35.00 Copyright © 2001 by Academic Press All rights of reproduction in any form reserved.