QUANTITATIVE-DETERMINATION OF PENTANE IN EXHALED AIR CORRELATES WITH COLONIC INFLAMMATION IN THE RAT COLITIS MODEL

Oxygen radicals play a key role in inflammation and inflammatory tissu e damage. Quantitative determination of pentane, a hydrocarbon generat ed by membrane lipid peroxidation initiated by oxygen radicals, in exp ired air has been used as a noninvasive determinant or index of inflam mation in various conditions. Herein we report the first examination o f the relationship between exhaled pentane and colonic inflammation in a rodent model of colitis. Colitis was induced in rats (n = 33) using the trinitrobenzene-sulfonic acid (TNB) model of colitis. Exhaled air was collected in a closed chamber on randomly selected animals on day s 1, 2, 4, 7, 11, 13, 15, 20, and 25 post-TNB treatment, and pentane w as assayed by means of gas chromatography. Gross and microscopic evide nce of inflammation was compared with exhaled pentane levels. Pentane levels varied from 0.0 to 14.6 nmol/l of air and were significantly in creased in TNB-treated rats compared with control rats only on days 7 to 15 after treatment (P < 0.05). Gross inspection showed severe colon ic inflammation through the first week (mean score = 4.7 out of a poss ible 5), persistent inflammation on days 7 to 15 (3.2), and healing an d fibrosis from the end of week two until day 25 (1.9 to 0). Histologi c evaluation confirmed a progression of inflammation from acute ulcera tion to chronic inflammation to fibrosis and scarring. We have demonst rated that pentane exhalation is increased after the induction of colo nic inflammation, with a seven-day lag time, and returns rapidly to no rmal as acute inflammation resolves. This suggests that pentane exhala tion can be used as a noninvasive measure of colonic inflammation in r odent models of colitis and perhaps clinically in humans.