Quinolone arthropathy in juvenile New Zealand white rabbits.

Twenty juvenile New Zealand white rabbits were dosed orally once daily with 1,000 mg of nalidixic acid/kg for 3, 7, and 14 consecutive days, then for 14 days followed by a 14-day recovery period. Eighteen age-matched rabbits were allotted to four groups and given corn oil vehicle to serve as controls for the various treatment durations. The articular cartilage from the stifle joints, shoulders, and elbows was studied by gross examination, light microscopy, and toluidine blue histochemistry, and the hips were studied by gross examination and transmission electron microscopy. When examined grossly, raised vesicles could be detected in the joints of some animals after 3 days of treatment. The distal portion of the femur and proximal portion of the ulna were predilection sites for gross lesions. Histologically, the vesicles were fluid-filled clefts in the intermediate layer of the articular cartilage. After 14 days, many of the lacunae in the areas of the defects contained chondrocyte clusters. When treated for 14 days and allowed a 14-day recovery period, territorial matrix had been deposited around individual chondrocytes within the clusters, compressing the matrix between the chondrocyte clusters into thin collagenous bands. For all treatment groups, decreased metachromasia, when stained with toluidine blue, provided histochemical evidence of loss of glycosaminoglycans in the matrix around the clefts.(ABSTRACT TRUNCATED AT 250 WORDS)