title: In vivo analysis of intestinal permeability following hemorrhagic shock.
abstract: OBJECTIVE
  To determine the time course of intestinal permeability changes to proteolytically-derived bowel peptides in experimental hemorrhagic shock.
  
  
  METHODS
  We injected fluorescently-conjugated casein protein into the small bowel of anesthetized Wistar rats prior to induction of experimental hemorrhagic shock. These molecules, which fluoresce when proteolytically cleaved, were used as markers for the ability of proteolytically cleaved intestinal products to access the central circulation. Blood was serially sampled to quantify the relative change in concentration of proteolytically-cleaved particles in the systemic circulation. To provide spatial resolution of their location, particles in the mesenteric microvasculature were imaged using in vivo intravital fluorescent microscopy. The experiments were then repeated using an alternate measurement technique, fluorescein isothiocyanate (FITC)-labeled dextrans 20, to semi-quantitatively verify the ability of bowel-derived low-molecular weight molecules (< 20 kD) to access the central circulation.
  
  
  RESULTS
  Results demonstrate a significant increase in systemic permeability to gut-derived peptides within 20 min after induction of hemorrhage (1.11 ± 0.19 vs 0.86 ± 0.07, P < 0.05) compared to control animals. Reperfusion resulted in a second, sustained increase in systemic permeability to gut-derived peptides in hemorrhaged animals compared to controls (1.2 ± 0.18 vs 0.97 ± 0.1, P < 0.05). Intravital microscopy of the mesentery also showed marked accumulation of fluorescent particles in the microcirculation of hemorrhaged animals compared to controls. These results were replicated using FITC dextrans 20 [10.85 ± 6.52 vs 3.38 ± 1.11 fluorescent intensity units (× 10(5), P < 0.05, hemorrhagic shock vs controls)], confirming that small bowel ischemia in response to experimental hemorrhagic shock results in marked and early increases in gut membrane permeability.
  
  
  CONCLUSIONS
  Increased small bowel permeability in hemorrhagic shock may allow for systemic absorption of otherwise retained proteolytically-generated peptides, with consequent hemodynamic instability and remote organ failure.
authors.affiliation: Tom Alsaigh, Marisol Chang, Michael Richter, Rafi Mazor, Department of Bioengineering, the Institute of Engineering in Medicine, University of California San Diego, La Jolla, CA 92093-0412, United States.
authors.forename: Tom
authors.initials: T
authors.lastname: Alsaigh
authors.affiliation: Tom Alsaigh, Marisol Chang, Michael Richter, Rafi Mazor, Department of Bioengineering, the Institute of Engineering in Medicine, University of California San Diego, La Jolla, CA 92093-0412, United States.
authors.forename: Marisol
authors.initials: M
authors.lastname: Chang
authors.affiliation: Tom Alsaigh, Marisol Chang, Michael Richter, Rafi Mazor, Department of Bioengineering, the Institute of Engineering in Medicine, University of California San Diego, La Jolla, CA 92093-0412, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Richter
authors.affiliation: Tom Alsaigh, Marisol Chang, Michael Richter, Rafi Mazor, Department of Bioengineering, the Institute of Engineering in Medicine, University of California San Diego, La Jolla, CA 92093-0412, United States.
authors.forename: Rafi
authors.initials: R
authors.lastname: Mazor
authors.affiliation: Tom Alsaigh, Marisol Chang, Michael Richter, Rafi Mazor, Department of Bioengineering, the Institute of Engineering in Medicine, University of California San Diego, La Jolla, CA 92093-0412, United States.
authors.forename: Erik B
authors.initials: EB
authors.lastname: Kistler
keywords: Hemorrhagic shock; Microcirculation; Peptides; Proteolysis; Small bowel ischemia