#1 An in vivo permeability test protocol using iohexol to reduce and refine the use of laboratory rats in intestinal damage assessment
Assessment of intestinal damage in laboratory rats with experimentally-induced enteropathies is usually carried out by collecting and morphological interpreting tissue samples obtained surgically, endoscopically or at necropsy. Alternatively, changes in the gut mucosa may be less invasively evaluated with intestinal permeability (IP) tests. In contrast to human and veterinary patients, IP test protocols in laboratory rats have been highly variable, which may account for the limited use of this approach by investigators when evaluating intestinal damage. The objective of this study was to establish a refined IP test protocol using iohexol in rats that is able to differentiate between healthy rats and individuals with enteropathies. Iohexol was administered by oral gavage to twenty-eight Sprague-Dawley rats, before and after the induction of inflammatory bowel disease (IBD) with dextran sulphate sodium (DSS). Urine was cumulatively recovered during 24 h, and the presence of iohexol was measured by high-performance liquid chromatography with ultraviolet detection. The median percentage (and interquartile range) of administered iohexol in urine of healthy rats was 0.54% (0.36–0.75%), whereas the respective value in rats with enteropathies was 11.42% (5.58–15.37%). The significant difference (P < 0.001) in the urinary recovery of iohexol demonstrated sufficient sensitivity of the test protocol to clearly discriminate between healthy and affected rats.
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