Effect of steroidal anti-inflammatory drugs on Escherichia coli endotoxin-induced mastitis in the cow.

Effects of intramammary infusion of prednisolone (40 mg) or intramuscular injection of dexamethasone (30 mg) or flumethasone (5 mg) on local and systemic signs in Escherichia coli endotoxin-induced mastitis were studied. The effect of varying intervals (0, 2, and 4 h) between intramammary infusion of endotoxin and prednisolone in the same quarter was determined. Intramammary infusion of endotoxin (.01 mg lipopolysaccharide of E. coli) produced inflammation of the infused quarter, fever, tachycardia, and leukopenia followed by a neutrophilic leukocytosis in the blood and a decrease in plasma zinc and iron concentrations. All corticosteroid treatments, except intramammary administration of prednisolone 4 h after endotoxin infusion, enhanced leukocytosis and diminished local signs of inflammation. Intramuscular injection of dexamethasone or flumethasone together with intramammary infusion of endotoxin and intramammary administration of prednisolone 2 h after lipopolysaccharide infusion completely abolished the febrile response. Abolishment of fever and attenuation of several hematologic and blood biochemical changes may be explained by diminished synthesis of endogenous mediators within the inflamed quarters due to glucocorticosteroid action.