CONSTRICTOR EFFECT OF COTTON BRACT EXTRACT ON ISOLATED CANINE AIRWAYS

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Abstract
Byssinosis is an occupational disease of textile workers that is attributed to the effect of cotton dust on the lung. Tissue bath techniques were used to examine the effects of cotton bract extract (CBE) on isolated canine airways. The CBE elicited strong contractions that were abolished by the 5-hydroxytryptamine (5-HT) antagonist, methysergide (3 .times. 10-6 M), but were only slightly affected by atropine (5 .times. 10-7 M) and pyrilamine (3 .times. 10-6 M). Desensitization to repeated exposures to CBE was not observed, and maximal contractions were equal in force to those produced by supramaximal electrical stimulation (15 V, 25 Hz, 0.5 ms pulse duration). Responses to exogenous 5-HT were qualitatively and quantitatively similar to those produced by CBE. Partial purification of CBE by Amicon ultrafiltration yielded a bronchoactive fraction containing low MW compounds (< 500). Analysis of the 5-HT concentration in this fraction by high-pressure liquid chromatography, fluorescence and column chromatography indicated that the amount of 5-HT present accounted for only 8-25% of the smooth-muscle-contracting activity of CBE. Cotton bracts apparently contain a potent 5-HT receptor agonist that appears to be distinct from 5-HT.

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