[Studies of adenosine inhalation in asthmatic patients]

In order to determine the mechanism of bronchoconstriction induced by the inhalation of adenosine in asthmatics, we measured, by the astograph method, cyclic nucleotides, leukotrienes and thromboxane B2 before and after the inhalation, and we studied the relationship between serum theophylline concentration and Rrs cont, Dmin and S Grs/Grs cont of the astogram obtained by inhaled adenosine. Plasma TXB2 level was significantly raised (p less than 0.05) after inhalation, but cAMP, cGMP, LTB4 and LTC4 did not change. In the astogram, Dmin was significantly elevated (p less than 0.01) when plasma theophylline concentration was raised to the therapeutic level, but Rrs cont and S Grs/Grs cont showed no remarkable change. We confirmed that inhaled adenosine caused bronchoconstriction in asthmatic patients, and that Dmin was elevated after the administration of theophylline. These results suggest that TXB2, a metabolic product of arachidonic acid, may be one of the most important mediators in the bronchoconstriction mechanism of inhaled adenosine.