Role of prostaglandins, histamine, and serotonin in the pathophysiology induced by Pasteurella hemolytica endotoxin in sheep.

Pasteurella hemolytica endotoxin (12 micrograms/kg) was infused intravenously into ewes over 500 min. Blood was sampled for 60 min before the infusion and at intervals during the infusion and for 1500 min postinfusion. The control values for plasma TxB2, 6-keto-PGF1 alpha, PGF2 alpha, and serotonin were 283 +/- 53 pg/ml (mean +/- standard error of mean), 281 +/- 14 pg/ml, 199 +/- 27 pg/ml, and 56.8 +/- 2.0 ng/ml, respectively. The plasma concentrations of TxB2, 6-keto-PGF1 alpha, PGF2 alpha, and serotonin significantly increased to a maximum at 50 min of infusion to 359%, 344%, 313%, and 201% of the control, respectively. PGF2 alpha and TxB2 returned to control levels at 300 min during infusion and 6-keto-PGF1 alpha at 60 min postinfusion and serotonin at 100 min of infusion. Serotonin concentration decreased significantly at 450 min of infusion to 73% of control and returned to control level at 1500 min postinfusion. No significant changes were found in the plasma levels of PGE, histamine, and ACE activity. We conclude that release of TxA2, PGI2, PGF2 alpha, and serotonin may contribute to pathophysiology induced by P. hemolytica endotoxin in sheep.