Preventive effects of theophylline on anaphylactic shock in rats.

Abstract

Anaphylactic shock was induced by administration of ovalbumin to sensitized rats. Preventive effects of theophylline on anaphylactic shock were examined with regard to the relationship between cAMP and prostaglandin (PG)E2 in lung tissue and plasma histamine. During anaphylactic shock, levels of cAMP content and PGE2 content in lung tissue decreased, while plasma histamine content increased. Theophylline increased levels of cAMP content and PGE2 content in lung tissue, in a dose-dependent manner, and pretreatment of animals with theophylline prevented the onset of anaphylactic shock. Pretreatment with indomethacin abolished the preventive effects of theophylline on anaphylactic shock and the effect of theophylline on the cAMP content. Dibutyryl cAMP (DBcAMP) increased PGE2 content in lung tissue, in a dose dependent manner, and prevented the onset of anaphylactic shock. These effects of DBcAMP were inhibited by the pretreatment with indomethacin, and cAMP in lung tissue was maintained at a high level. In the group in which anaphylactic shock was prevented, PGE2 content in lung tissue was significantly high in all cases. PGE2 infusion prevented anaphylactic shock. Theophylline may increase cAMP levels in lung tissue only in the presence of endogenous PG. Increased cAMP content in lung tissue may subsequently increase PGE2 content in lung tissue. Preventive effects of theophylline on anaphylactic shock may be due to increased PGE2 content in lung tissue.