Interaction of thromboxane A2 and tissue pathology during graded bacteremia

The purpose of this study was to determine whether or not thromboxane A2 (TXA2) was necessary or sufficient for the development of end-organ pathology during graded bacteremia. Pulmonary artery catheters were placed in 21 adult male pigs under pentobarbital anesthesia and breathing room air. After a control period, animals were studied in four groups: Group 1, anesthesia only; Group 2, infusion of 1 X 10(9) ml Aeromonas hydrophila which was gradually increased from 0.2 ml/kg/hr to 4.0 ml/kg/hr over 4 hours; Group 3, pretreatment with SQ 29,548 (TXA2 antagonist) then Aeromonas h. infusion; Group 4, infusion of U46619 (TXA2 agonist) to pulmonary artery pressures measured in Group 2. Animals were sacrificed after 4 hours and the lungs, liver, spleen, kidneys, and heart were examined under light microscopy by a pathologist unaware of study groups. The results indicated that physiologic thromboxane A2 agonist (Group 4) was sufficient alone to cause pulmonary inflammation. Thromboxane A2 was neither necessary nor sufficient for significant renal, hepatic, pulmonary, or splenic pathology to occur in graded bacteremia, manifested in similar microanatomic abnormalities in these organs in Groups 2 and 3 and in Groups 1 and 4. Pulmonary leukocyte infiltration was significantly increased in Group 3 compared to all other groups, suggesting that TXA2 impairs inflammatory responses.