Sustained inhibition of antigen-induced histamine release from human lung by the beta 2-adrenoceptor agonist terbutaline

Antigen-induced histamine release from passively sensitized human lung tissue was inhibited in the presence of the beta 2-adrenoceptor agonist, terbutaline. A sustained and statistically significant suppression was detected in the concentration interval 3 X 10(-8)-1 X 10(-6) M. Fifty per cent inhibition IC50, was obtained at an interpolated concentration of 5.3 X 10(-8) +/- 0.4 X 10(-8) M (n = 13), when the histamine secretion was elicited with optimum concentration of antigen. Histamine release induced with a suboptimum concentration of antigen was inhibited to a greater extent than release initiated with optimum concentration. The data in the present investigation support the concept that terbutaline-induced inhibition of mediator release from human lung tissue can contribute to the clinical effectiveness of the drug during treatment of allergic asthma.

A new in vivo method for the measurement of repetitive anaphylactic responses in the guinea-pig

The established Konzett-Rossler bronchorespiratory model has been combined with a unique ovalbumin sensitization procedure to give a novel method to measure anaphylaxis in the anaesthetized guinea-pig. Following antigen challenge, up to eight equal bronchoconstrictor responses to the same dose can be generated from a single animal over a 120 min period. Total inhibition of the anaphylactic response can be elicited by four different classes of compound, namely salbutamol, mepyramine, theophylline and dimaprit. Cromoglycate failed to cause any inhibition. The method is discussed with particular reference to the antigen sensitization procedure, which differs substantially from other regimens previously employed and gives rise to heat labile antibody.