HISTOLOGICAL EXAMINATION ON ACHILLES-TENDON LESIONS INDUCED BY QUINOLONE ANTIBACTERIAL AGENTS IN JUVENILE RATS

We examined the effects of the quinolone antibacterial agents pefloxac in (PFLX) and ofloxacin (OFLX) on the Achilles tendon of Sprague-Dawle y rats. A single oral administration of PFLX 300 and 900 mg/kg or OFLX 900 mg/kg induced edema with mononuclear cell infiltration mainly in the inner sheath of the inner Achilles tendon just proximal to the tub er calcanei in rats killed on the next day. Cell infiltration was also seen in the adjacent synovial membrane and joint space. With progress ion of severity, the lesions extended to the surface tendon tissue, wh erein irregularly arranged collagen bundles were detached from each ot her and nuclei of fibroblasts were pyknotic and fragmented. After 2-wk repeated administration, these lesions were replaced by fibrotic foci with regenerated tendon fibroblasts, and the incidence and severity w ere reduced in the OFLX but not PFLX groups. Coadministration of cyclo sporin A with OFLX 300 mg/kg induced these lesions despite the fact th at neither induced lesions alone. The tendon lesions were induced in j uvenile rats (4 wk of age) but not in young adults (12 wk). The articu lar cartilage of juvenile rats showed focal degeneration and/or cavita tion in the tarsal joints after a single and 2-wk administration of PF LX or OFLX. Hydrocortisone slightly increased the incidence of OFLX-in duced lesions in both the tendon and cartilage after a 2-wk administra tion. The occurrence of the tendon lesions is different from that of t he Achilles tendon disorders reported in older humans, but they are th ought to be a useful model for them.