Role of prostaglandins in pathogenesis of bovine mastitis induced by Escherichia coli endotoxin.

Four doses (5 to 100 micrograms, 1 dose/quarter) of Escherichia coli endotoxin were introduced into lactating mammary glands of 2 cows. There was no effect on milk prostaglandin (PG) E2 concentration, except that the concentration was increased from 200 pg/ml of milk to 1,060 pg/ml at post-treatment hour (PTH) 8 in cow 1 and from 75 to 420 pg/ml at PTH 4 in cow 2 after the highest dose 100 micrograms. Endotoxin caused a dose-dependent increase in milk PGF2 alpha concentrations in both cows. After the highest dose, PGF2 alpha was maximally increased from 200 to 3,500 pg/ml at PTH 4 in cow 1 and from 250 to 2,000 pg/ml in cow 2 at PTH 8. The instillation of 50 micrograms of endotoxin in all 8 quarters of 2 more lactating cows caused no significant (P greater than 0.05) changes in milk PGE2 and thromboxane B2 concentrations, whereas milk PGF2 alpha was significantly increased from the base-line value of 642 to 2,683, 1,189, and 2,281 pg/ml at PTH 4, 8, and 12, respectively. The 6-keto-PGF1 alpha was also significantly increased from the base-line value of 305 to 871, 631, and 600 pg/ml at the corresponding times, respectively. A marked increase in vascular permeability, as judged by high concentrations of serum albumin in the whey, was observed as early as PTH 4 and peaked at PTH 12 followed by a gradual decline, although it remained significantly increased over the control for 48 hours after treatment.(ABSTRACT TRUNCATED AT 250 WORDS)