PROSTAGLANDIN E₂ AND CYCLIC NUCLEOTIDES DURING ANAPHYLACTIC SHOCK IN RATS

Abstract

Anaphylactic shock was induced with ovalbumin in sensitized rats and the relationship between PGE₂ and cyclic nucleotides in lung tissue and plasma histamine during anaphylactic shock was studied. PGE₂ level and cyclic AMP/cyclic GMP ratio decreased with this ovalbumin-challenge, and the former reached a minimum value 40 sec after the challenge while the latter reached a minimum value 20 sec later. The plasma histamine level was elevated and reached a maximum value concomitant with the minimum value in the cyclic AMP/cyclic GMP ratio. Dibutyryl cyclic AMP elevated the PGE₂ level significantly and inhibited the ovalbumin-induced elevation of plasma histamine, however, this effect was abolished by the administration of indomethacin. PGE₂ infusion elevated the cyclic AMP level as well as the cyclic AMP/cyclic GMP ratio, in a time-dependent manner, and inhibited the oval burnin-induced elevation of plasma histamine during 10 min infusion. There was a significant correlation between the cyclic AMP level and the cyclic AMP/cyclic GMP ratio, both elevated by PGE₂ infusion. Thus, anaphylactic elevation of the plasma histamine level results from a decrease in the levels of PGE₂ in lung tissue rather than a decrease in the cyclic AMP/cyclic GMP ratio, albeit these decreases being coincident during anaphylactic shock.