The relation between effects of adenosine, theophylline and enprofylline on the contractility of sensitized guinea-pig lung strips

Abstract

Abstract Contractile responses of lung parenchymal strips from ovalbumin-sensitized guinea-pigs to cumulative addition of antigen were significantly potentiated by 10 min pretreatment with adenosine 10 μM. This potentiation was unaffected by the adenosine uptake inhibitor, dipyridamole, 2 μM. Cumulative addition of adenosine 0ṁ1–100 μM to parenchymal strips without antigen produced variable responses, unrelated to sensitization, some contracting, some relaxing. Theophylline 100 μM caused relaxation of parenchymal strips and significantly inhibited the antigen-induced contraction with a parallel shift of the log concentration-response line. It also inhibited the adenosine-induced potentiation of contraction. Enprofylline 100 μM caused a greater relaxation of the tissue than theophylline. While it inhibited the adenosine-induced potentiation of the response, enprofylline, in contrast to theophylline, failed to inhibit the antigen-induced contraction of guinea-pig parenchyma. At these concentrations, theophylline and enprofylline each inhibited the antigen-induced release of SRSA (leukotrienes C4, D4 and E4), and of histamine, from sensitized guinea-pig lung fragments.