Aggregate anaphylaxis in the monkey: attenuation of the pulmonary response by pretreatment with indomethacin.

Aggregate anaphylaxis (anaphylaxis mediated by circulating antibodies) in Macaca irus monkeys causes aggregation of platelets in the lungs, a marked increase in pulmonary vascular resistance, and a decrease in cardiac output. In the present study, the effect of pretreatment with indomethacin (10 mg/kg, n = 5) was studied in this type of anaphylaxis. Compared with untreated animals, the pulmonary vascular and airway reaction was considerably attenuated after pretreatment with indomethacin. Pulmonary vascular resistance increased twofold as against tenfold in untreated animals, and no increase in pulmonary resistance to gas flow was observed as against a twofold increase in the untreated group. In the indomethacin group, cardiac output decreased by a mean of 36% as against 75% in the untreated group. Both right and left atrial pressures decreased and the hemodynamic pattern is compatible with relative hypovolemia. These results suggest that prostaglandin-like substances play an important part in the initial phase of aggregate anaphylaxis in the monkey.