Objective—To determine the effects of oxytetracycline
on matrix metalloproteinase-1 (MMP-1) mRNA
expression and collagen gel contraction by equine
myofibroblasts in an effort to explain the mechanistic
basis for the pharmacologic treatment of flexural
deformities in foals.
Sample Population—Cultured myofibroblasts from
the accessory ligament (distal check ligament) of 6
Procedure—Collagen gel scaffolds seeded with
equine myofibroblasts were cultured in individual culture
dishes containing complete media (Dulbecco's
modified Eagle medium with 10% fetal bovine serum)
and oxytetracycline (0, 12.5, 25, or 75 µg/mL) for 48
hours. After 24 hours, the gels were released from
the bottom of the culture plate and allowed to contract.
Photographs were taken at 0, 1, 2, 4, 6, 8, and
24 hours after release to assess the degree of collagen
gel contraction. Additional gels were harvested at
2 hours after release for RNA isolation and reverse
transcriptase-polymerase chain reaction assessment
of the degree of MMP-1 mRNA expression.
Results—Oxytetracycline induced a dose-dependent
inhibition of collagen gel contraction by equine myofibroblasts.
Oxytetracycline also induced a dose-dependent
decrease in MMP-1 mRNA expression by equine
Conclusions and Clinical Relevance—Results of
this study indicate that oxytetracycline inhibits tractional
structuring of collagen fibrils by equine myofibroblasts
through an MMP-1 mediated mechanism. In
young foals, oxytetracycline administration may make
the developing ligaments and tendons more susceptible
to elongation during normal weight-bearing.
Inhibition of normal collagen organization may provide
the mechanistic explanation for the results seen following
the pharmacologic treatment of flexural deformities
in foals by oxytetracycline administration. (Am
J Vet Res 2004;65:491–496)
To compare the pharmacokinetics of cefquinome sulfate in ducklings and goslings after IV or IM administration of a single dose.
216 healthy Muscovy ducklings (Cairina moschata) and 216 healthy Sichuan white goslings (Anser cygnoides).
Ducklings and goslings were each randomly assigned to 3 groups (n = 72/group) that received a single dose (2 mg/kg) of injectable cefquinome sulfate administered IV or IM or of injectable cefquinome sulfate suspension administered IM. Blood samples were collected at various points after drug administration (n = 6 birds/time point). Plasma cefquinome concentrations were measured by high-performance liquid chromatography with UV detection, and pharmacokinetic parameters were calculated with a 2-compartment model method.
After IV injection, mean distribution half-life of cefquinome was longer in goslings (0.446 hours) than in ducklings (0.019 hours), whereas volume of distribution at steady state was greater (0.432 vs 0.042 L/kg) and elimination half-life was slower (1.737 vs 0.972 hours). After IM administration of injectable cefquinome sulfate, bioavailability of the drug was higher in goslings (113.9%) than in ducklings (67.5%). After IM administration of injectable cefquinome sulfate suspension, bioavailability was also higher in goslings (123.1%) than in ducklings (96.8%), whereas elimination half-life was slower (6.917 vs 1.895 hours, respectively).
CONCLUSIONS AND CLINICAL RELEVANCE
In goslings, IV administration of cefquinome resulted in slower distribution and metabolism of the drug than in ducklings and IM administration resulted in higher bioavailability. The delayed-release effect of the injectable cefquinome sulfate suspension when administered IM was observed only in goslings.