Prostaglandin E2 and cyclic nucleotides during anaphylactic shock in rats.

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 ovalbumin-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.