Objective—To characterize gelatinases in bronchoalveolar
lavage fluid (BALF) and gelatinases produced
by alveolar macrophages of healthy calves.
Sample Population—Samples of BALF and alveolar
macrophages obtained from 20 healthy 2-month-old
Procedure—BALF was examined by use of gelatin
zymography and immunoblotting to detect gelatinases
and tissue inhibitor of metalloproteinase (TIMP)-1
and -2. Cultured alveolar macrophages were stimulated
with lipopolysaccharide (LPS), and conditioned
medium was subjected to zymography. Alveolar
macrophage RNA was used for reverse transcriptasepolymerase
chain reaction assay of matrix metalloproteinases
(MMPs), cyclooxygenase-2, and inducible
nitric oxide synthase.
Results—Gelatinolytic activity in BALF was evident at
92 kd (14/20 calves; latent MMP-9) and 72 kd (18/20;
latent MMP-2). Gelatinolytic activity was evident at 82
kd (10/20 calves; active MMP-9) and 62 kd (17/20;
active MMP-2). Gelatinases were inhibited by metal
chelators but not serine protease inhibitors.
Immunoblotting of BALF protein and conditioned
medium confirmed the MMP-2 and -9 proteins.
Endogenous inhibitors (ie, TIMPs) were detected in
BALF from all calves (TIMP-1) or BALF from only 4
calves (TIMP-2). Cultured alveolar macrophages
expressed detectable amounts of MMP-9 mRNA but
not MMP-2 mRNA.
Conclusions and Clinical Relevance—Healthy
calves have detectable amounts of the gelatinases
MMP-2 and -9 in BALF. Endogenous inhibitors of
MMPs were detected in BALF (ie, TIMP-1, all calves;
TIMP-2, 4 calves). Lipopolysaccharide-stimulated alveolar
macrophages express MMP-9 but not MMP-2
mRNA. The role of proteases in the pathogenesis of
lung injury associated with pneumonia has yet to be
determined. (Am J Vet Res 2004;65:163–172)
OBJECTIVE To determine the effect of age on the pharmacokinetics and pharmacodynamics of flunixin meglumine following IV and transdermal administration to calves.
ANIMALS 8 healthy weaned Holstein bull calves.
PROCEDURES At 2 months of age, all calves received an injectable solution of flunixin (2.2 mg/kg, IV); then, after a 10-day washout period, calves received a topical formulation of flunixin (3.33 mg/kg, transdermally). Blood samples were collected at predetermined times before and for 48 and 72 hours, respectively, after IV and transdermal administration. At 8 months of age, the experimental protocol was repeated except calves received flunixin by the transdermal route first. Plasma flunixin concentrations were determined by liquid chromatography-tandem mass spectroscopy. For each administration route, pharmacokinetic parameters were determined by noncompartmental methods and compared between the 2 ages. Plasma prostaglandin (PG) E2 concentration was determined with an ELISA. The effect of age on the percentage change in PGE2 concentration was assessed with repeated-measures analysis. The half maximal inhibitory concentration of flunixin on PGE2 concentration was determined by nonlinear regression.
RESULTS Following IV administration, the mean half-life, area under the plasma concentration-time curve, and residence time were lower and the mean clearance was higher for calves at 8 months of age than at 2 months of age. Following transdermal administration, the mean maximum plasma drug concentration was lower and the mean absorption time and residence time were higher for calves at 8 months of age than at 2 months of age. The half maximal inhibitory concentration of flunixin on PGE2 concentration at 8 months of age was significantly higher than at 2 months of age. Age was not associated with the percentage change in PGE2 concentration following IV or transdermal flunixin administration.
CONCLUSIONS AND CLINICAL RELEVANCE In calves, the clearance of flunixin at 2 months of age was slower than that at 8 months of age following IV administration. Flunixin administration to calves may require age-related adjustments to the dose and dosing interval and an extended withdrawal interval.