IMMUNOHISTOCHEMISTRY OF ARTICULAR-CARTILAGE FROM IMMATURE BEAGLE DOGSDOSED WITH DIFLOXACIN

Effects of the fluoroquinolone difloxacin on articular-epiphyseal cart ilage in growing beagle dogs have been described by light microscopic, electron microscopic, and biochemical methods. Here we present data f rom an immunohistochemistry study with humeral head cartilage from 3-m o-old beagle dogs after treatment with 1 or 2 oral doses of 300 mg dif loxacin/kg body weight. Dogs were euthanatized either 24 hr (single do se) or 48 hr (2 doses) after onset of dosing, and cartilage tissue was stored at -90 degrees C until it was studied by immunohistochemistry. Antibodies against matrix components (collagen II, fibronectin) as we ll as antibodies against cellular structures (integrins) were used. Af ter single-dose treatment (24-hr group:), cartilage lesions such as cl efts were not observed, but increased staining for fibronectin was fou nd in cartilage samples from 5 of 6 animals. Markedly increased staini ng for fibronectin was also demonstrated in the vicinity of clefts wit hin cartilage of all animals of the 48-hr group. Collagen II staining was homogeneously distributed in cartilage from controls and was sligh tly reduced in territorial matrix in 2 of 6 dogs of the 48-hr group. I ntegrin staining on chondrocytes was nor significantly affected by dif loxacin under the given conditions with the exception of a slight redu ction of the or, integrin chain in 1 of 5 dogs of the 48-hr group. Ove rall, the most important result is the finding that fibronectin was a sensitive immunohistochemical marker for change in cartilage samples d ue to difloxacin treatment in dogs.