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In Vitro and In Vivo Reactivity Changes in Guinea Pig Airway Smooth Muscle in Response to Challenges from Heat- Treated and Untreated Cotton Dust Extract

R.S. Young, P. J. Nicholls


As part of an investigation into the effect of the heat detoxification of cotton dust1 in vitro and in vivo experiments were carried out to compare the toxicological potential of inhaled aqueous cotton dust extracts (CDEs). The in vitro work, carried out on both tracheal spiral and perfused lung preparations, demonstrated a phase of hyperresponsiveness due to the action of both types of dust extract. The hyperresponsiveness manifests itself as a leftward shift in the dose - response curve of the standard bronchoconstrictor. The degree of shift was ten - fold in the case of the untreated dust and one and a half - fold for the heat - treated dust. The hyperresponsiveness was not significantly affected by any of the pharmacological agents (atropine, chlopheniramine, FPL 55712 or indomethacin) except in the case of the TXA2 antagonist OKY048. Comparisons are made with results obtained from similar work with pure lipopolysaccharides (LPS).

In vivo, using a whole animal restrained plethysmographic method, hyperresponsiveness to the dust extract was developed approximately 1h post exposure. The reactivity change developed in the case of both dust types but the degree to which the change occurred varied, the untreated dust being more able to induce a reactivity change (20%) compared to change of 15% with the heat - treated dust. The result correlates well with the time taken to induce a hyperresponsive change as seen with pure LPS. However, the overall percentage change in reactivity was not as great with the dust extracts, the change being on average 17% compared with a 30% reduction with the pure LPS.

The heat treatment protocol may therefore be regarded as a detoxification process although complete detoxification of the extract does not occur. Although LPS has been shown, both directly and indirectly, to be a major contributor to the induction of hyperresponsiveness in guinea pig airways; other components present in the extracts may also play an important contributory role e.g. tannins, glucans.

Reprinted from Proceedings of the 1996 Beltwide Cotton Conferences pp. 319 - 323
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998