Concentrations of
tumor necrosis factor-alpha (
TNF-alpha) and of NO(x) (sum of
nitrite and
nitrate as indicators of endogenous
nitric oxide production) in milk and blood plasma were measured in three
mastitis models in dairy cows in early lactation. Escherichia coli P4:O37 bacteria or
endotoxin O111:B4 were administered into both left quarters of 12 and 6 cows, respectively. Six of the E. coli-infected cows were treated with a bactericidal
antibiotic (
Enrofloxacin; Bayer AG, Leverkusen, Germany) i.v.
at 10 hr and subcutaneously (sc) at 30 hr after
infection. NO(x) concentrations transiently increased maximally 10- to 11-fold in milk of E. coli-infected quarters with or without
antibiotic treatment at 24 hr and after
endotoxin administration. NO(x) concentrations did not change in milk of unchallenged quarters and in blood plasma. Increases of NO(x) were proceeded by a transient (96- to 149-fold) rise of milk
TNF-alpha concentrations, which in
endotoxin-administered quarters was maximal at 6 hr and in infected quarters without or with
Enrofloxacin treatment
at 10 and 14 hr. In blood plasma
TNF-alpha concentrations only moderately increased to peaks in
endotoxin-administered cows at 6 hr and in E. coli-infected cows at 14 hr postchallenge. In one severely sick, nontreated E. coli-infected cow milk,
TNF-alpha response at 14 hr was excessive and followed by a spectacular rise of NO(x) concentration in milk between 48 and 72 hr. In conclusion, a possible clinical relevance of
nitric oxide production associated with a rise of intramammary and systemic
TNF-alpha during acute
mastitis by E. coli
infection and
endotoxin in lactating dairy cows is indicated, but could not be inhibited by
antibiotic treatment.