Objective—To establish an in vitro assay and determine
the differential suppressive activity of non
steroidal anti-inflammatory drugs (NSAID) on cyclooxygenase
(COX)-1 and COX-2 isoenzymes in dogs.
Procedure—COX activity was evaluated in the presence
and absence of 4 NSAID (meloxicam, tolfenamic
acid, carprofen, and ketoprofen), using a canine
monocyte/macrophage cell line that constitutively
expresses COX-1, but can be induced to express
COX-2 when incubated with lipopolysaccharide.
Inhibition of prostaglandin E2 (PGE2) synthesis by
each NSAID was measured by enzyme immunoassay
and attributed to specific COX-1 or COX-2 activity
through assessment of COX messenger RNA expression
by use of northern blot analysis and reverse transcription-
polymerase chain reaction (RT-PCR). The
COX selectivity of each drug was evaluated from
dose-response curves by calculating a ratio (COX-
1:COX-2) of inhibitory concentration values on the
basis of concentrations that reduced PGE2 by 50% in
each COX model.
Results—Meloxicam and tolfenamic acid preferentially
inhibited COX-2, with meloxicam inhibiting COX-2
activity 12 times more effectively than COX-1 activity.
Carprofen was only 1.75 times more selective for
COX-2 than for COX-1, and ketoprofen was slightly
more selective for COX-1.
Conclusions—COX-1 and COX-2 were differentially
sensitive to inhibition in vitro by NSAID.
Meloxicam and tolfenamic acid were selective for
COX-2. Effects of carprofen and ketoprofen
approached equipotency against both isoenzymes.
Selective COX-2 inhibitors are a new class of drugs
with anti-inflammatory effects similar to conventional
NSAID but with fewer adverse effects.
Development of these agents for veterinary use
would be facilitated by the convenience of using a
canine cell line as a model system to screen COX-
1 and COX-2 inhibitor activities in vitro. (Am J Vet
Objective—To examine cyclooxygenase (COX)
expression in canine platelets and Madin-Darby
canine kidney (MDCK) cells in culture.
Sample Population—Canine platelets and MDCK cells.
Procedure—Total RNA was recovered from isolated
canine platelets and MDCK cells. Northern blot analysis
and reverse transcription-polymerase chain reaction (RTPCR),
using complementary DNA probes and primers
designed from the human COX sequences, were used
to determine COX-1 and -2 (cyclooxygenase isoforms 1
and 2) messenger RNA (mRNA) expression.
Results—Following northern blot analysis, canine
platelets were found to express only the 2.8-kb COX-
1 transcript; COX-2 was not detected. Canine MDCK
cells expressed the 4.5-kb COX-2 transcript, in addition
to the 2.8-kb COX-1 transcript. A single DNA
band of 270 base pairs was identified following gel
electrophoresis of the product obtained from RT-PCR
of mRNA from canine platelets. Sequencing revealed
that this PCR product was 90% homologous to a portion
of the human COX-1 gene (Genbank M59979).
Conclusions and Clinical Relevance—Detection of
COX-1 by RT-PCR of RNA obtained from canine
platelets is a novel finding. The 90% homology of the
PCR product with the human sequence suggests
strong conservation between the canine and human
COX-1 gene. Cloning and sequencing of the canine
gene will be required to fully characterize homologous
regions. Because of the importance of COX in the
inflammatory process and as a potential target of currently
available nonsteroidal anti-inflammatory drugs
(NSAID), a better understanding of canine COX may
improve our ability to use NSAID appropriately,
achieve efficacy, and avoid potential adverse drug
effects in dogs. (Am J Vet Res 2000;61:1512–1516)
Objective—To determine whether inflammation of the jejunum of horses decreases the number of motilin receptors and amounts of motilin receptor mRNA and alters erythromycin lactobionate binding affinity to the motilin receptor in jejunal tissues.
Sample Population—Jejunal segments in 6 adult horses.
Procedure—Each horse was anesthetized, and a ventral median celiotomy was performed; 2 segments of jejunum underwent a sham operation, 2 segments underwent ischemic strangulation obstruction (ISO), and 2 segments underwent intraluminal distension (ILD). Treatments were maintained for 120 minutes. From each segment, full-thickness biopsy samples were collected and smooth-muscle homogenates were prepared. Affinity and distribution of motilin binding to these preparations were determined by use of iodine 125 (125I)-labeled synthetic porcine motilin. Via displacement experiments, competition between 125I-labeled motilin and erythromycin lactobionate for binding to motilin receptors in the different segments was investigated. A quantitative real-time PCR technique was used to assess motilin receptor mRNA content in the muscle preparations.
Results—Compared with the ISO or ILD segments, the number of motilin receptors was significantly higher in the sham-operated segments; ILD segments contained the lowest number of motilin receptors. The expression of motilin receptor mRNA was significantly decreased in ILD segments but not in ISO segments. Erythromycin lactobionate displacement of 125I-labeled motilin from motilin receptors did not differ significantly among the jejunal segments.
Conclusions and Clinical Relevance—Results suggest that downregulation and decreased production of motilin receptors in inflamed jejunal tissue contribute to the altered prokinetic response to erythromycin in horses with gastrointestinal disease.
Objective—To compare morphologic and morphometric features of the cervical vertebral column and spinal cord of Doberman Pinschers with and without clinical signs of cervical spondylomyelopathy (CSM; wobbler syndrome) detected via magnetic resonance imaging (MRI).
Animals—16 clinically normal and 16 CSM-affected Doberman Pinschers.
Procedures—For each dog, MRI of the cervical vertebral column (in neutral and traction positions) was performed. Morphologically, MRI abnormalities were classified according to a spinal cord compression scale. Foraminal stenosis and intervertebral disk degeneration and protrusion were also recorded. Morphometric measurements of the vertebral canal and spinal cord were obtained in sagittal and transverse MRI planes.
Results—4 of 16 clinically normal and 15 of 16 CSM-affected dogs had spinal cord compression. Twelve clinically normal and all CSM-affected dogs had disk degeneration. Foraminal stenosis was detected in 11 clinically normal and 14 CSM-affected dogs. Vertebral canal and spinal cord areas were consistently smaller in CSM-affected dogs, compared with clinically normal dogs. In neutral and traction positions, the intervertebral disks of CSM-affected dogs were wider than those of clinically normal dogs but the amount of disk distraction was similar between groups.
Conclusions and Clinical Relevance—The incidence of intervertebral disk degeneration and foraminal stenosis in clinically normal Doberman Pinschers was high; cervical spinal cord compression may be present without concurrent clinical signs. A combination of static factors (ie, a relatively stenotic vertebral canal and wider intervertebral disks) distinguished CSM-affected dogs from clinically normal dogs and appears to be a key feature in the pathogenesis of CSM.
Objective—To identify and characterize motilin receptors
in equine duodenum, jejunum, cecum, and large
colon and to determine whether erythromycin lactobionate
competes with porcine motilin for binding to
Sample Population—Specimens of various segments
of the intestinal tracts of 4 adult horses euthanatized for
reasons unrelated to gastrointestinal tract disease.
Procedure—Cellular membranes were prepared from
smooth muscle tissues of the duodenum, jejunum,
pelvic flexure, and cecum. Affinity and distribution of
motilin binding on membrane preparations were determined
by use of 125I-labeled synthetic porcine motilin.
Displacement studies were used to investigate competition
between 125I-labeled synthetic porcine motilin
and erythromycin lactobionate for binding to motilin
receptors in various segments of bowel.
Results—Affinity of 125I-labeled synthetic porcine motilin
for the equine motilin receptor was estimated to be
6.1nM. A significantly higher number of motilin receptors
was found in the duodenum than in the pelvic flexure
and cecum. The jejunum had a significantly higher
number of motilin receptors than the cecum.
Erythromycin lactobionate displacement of 125I-labeled
porcine motilin from the equine motilin receptor did not
differ significantly among various segments of bowel.
Conclusions and Clinical Relevance—Motilin receptors
were found in the duodenum, jejunum, pelvic
flexure, and cecum of horses. The highest number of
motilin receptors was in the duodenum, and it
decreased in more distal segments of bowel.
Erythromycin lactobionate competed with motilin
binding in the equine gastrointestinal tract. This suggests
that 1 of the prokinetic actions of erythromycin
in horses is likely to be secondary to binding on
motilin receptors. (Am J Vet Res 2002;63:1545–1550)
Objective—To determine effects of extracorporeal shock wave therapy (ESWT) on healing of wounds in the distal portion of the forelimb in horses.
Procedures—Five 6.25-cm2 superficial wounds were created over both third metacarpi of 6 horses. Forelimbs were randomly assigned to treatment (ESWT and bandage) or control (bandage only) groups. In treated limbs, each wound was treated with 625 shock wave pulses from an unfocused electrohydraulic shock wave generator. In control limbs, each wound received sham treatment. Wound appearance was recorded weekly as inflamed or healthy and scored for the amount of protruding granulation tissue. Standardized digital photographs were used to determine the area of neoepithelialization and absolute wound area. Biopsy was performed on 1 wound on each limb every week for 6 weeks to evaluate epithelialization, fibroplasia, neovascularization, and inflammation. Immunohistochemical staining for A smooth muscle actin was used to label myofibroblasts.
Results—Control wounds were 1.9 times as likely to appear inflamed, compared with treated wounds. Control wounds had significantly higher scores for exuberant granulation tissue. Treatment did not affect wound size or area of neoepithelialization. No significant difference was found for any of the histologic or immunohistochemical variables between groups.
Conclusions and Clinical Relevance—Treatment with ESWT did not accelerate healing of equine distal limb wounds, but treated wounds had less exuberant granulation tissue and appeared healthier than controls. Therefore, ESWT may be useful to prevent exuberant granulation tissue formation and chronic inflammation of such wounds, but further studies are necessary before recommending ESWT for clinical application.