The contractile or relaxant activities or both of aqueous extracts of green and roasted coffees were assayed on isolated guinea pig tracheal spirals. Contractile and relaxant activities were compared with histamine and theophylline, respectively. Green coffee extracts induced concentration dependent contraction, but the maximal tension never exceeded 76.3% +/- 5.2 of a maximal histamine contraction (0.69 +/- 0.07 g/mm2 v 0.52 +/- 0.05 g/mm2; p (0.01). One gram of green coffee dust had a biological activity equivalent to 1.23 +/- 0.1 mg of histamine. The pD2 value of histamine was -5.17 +/- 0.05. The potency of green coffee was unaffected by mepyramine maleate (1 micrograms/ml, final bath concentration) while that of histamine was reduced 500 fold. Tissues contracted with histamine were not significantly relaxed by green coffee extracts. By contrast, roasted coffee extracts induced concentration dependent relaxation of uncontracted and histamine contracted tissues. Tissues contracted with green coffee extracts were also completely relaxed by roasted coffee extracts. The pD2 value of theophylline was -4.10 +/- 0.03. The relaxant activity of 1 g of roasted coffee was equivalent to 1.95 +/- 0.16 mg of theophylline. The potency of these extracts was significantly reduced after propranolol (1 micrograms/ml; dose ratio 1.56). Our results show that coffee dust extracts have considerable biological activity which changes from a contractile to a relaxant action as a consequence of processing. The greater incidence of adverse reactions to green coffee dust(s) in coffee workers may be related to the contractile activity present in green coffee dust.
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