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  • Title: Influence of spasmogen inhalation by guinea pigs upon subsequent demonstration of ovalbumin-induced hyperreactivity in isolated airways tissues.
    Author: Lewis CA, Broadley KJ.
    Journal: J Pharmacol Toxicol Methods; 1995 Dec; 34(4):187-98. PubMed ID: 8785420.
    Abstract:
    Guinea pigs were sensitized with ovalbumin (i.p.) 14 days before use. In vivo airway hyperreactivity induced by ovalbumin inhalation was determined by challenging with aerosolized spasmogen (5-hydroxytryptamine [5-HT] methacholine, the thromboxane-mimetic, U-46619, or adenosine) 24 hr before (7 days with adenosine) and again 18-24 hr after the ovalbumin inhalation. One hour later they were killed and isolated airways perfused lung halves and tracheal spirals were set up for determination of tissue sensitivity to carbachol, histamine, and adenosine. This study examines whether the spasmogen interferes with the ovalbumin-induced in vitro hyperreactivity and the combined effects of ovalbumin followed by spasmogen challenge upon tissue sensitivity. The influence of the spasmogen upon the in vitro measurement of ovalbumin-induced hyperreactivity was variable, depending upon which spasmogen was used and whether the lung or trachea was examined. The inhalation of the spasmogen in ovalbumin-challenged guinea pigs had clear effects upon the subsequent measurement of tissue sensitivity. This depended upon the spasmogen used, but 5-HT, methacholine, and U-46619 usually depressed responsiveness, while adenosine was without significant effect. As a consequence, the appearances of in vitro hyperreactivity due to the ovalbumin challenge could be masked (e.g., bolus doses of agonist in the trachea when 5-HT was the spasmogen) or the degree of hyperreactivity could be enhanced (e.g., in the perfused lung when adenosine was the spasmogen). Thus, isolated airways tissues should not be used for evaluating tissue sensitivity when the animals have been previously exposed to inhalations of spasmogens.
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