Ocular toxicity caused by Paclitaxel in neonatal sprague-dawley rats.

BACKGROUND: The toxic effects of paclitaxel (PTX) on neonatal eyes have not been evaluated. MATERIALS AND METHODS: PTX was dissolved in solvent containing polyethoxylated castor oil and intraperitoneally administered to male and female Sprague-Dawley rats at a dose of 0, 2, 4 and 8 mg/kg at 0 day of age, 4 mg/kg at 14 days of age, or 8 mg/kg at 12-18 weeks of age. Eyes were histologically examined 1 and/or 7 days after PTX. RESULTS: Male and female rats that received 4 mg/kg or more of PTX at 0 days of age developed cataracts and retinal dysplasias, while the rats that received other dosing regimens did not develop ocular lesions. Epithelial cells in the lens were apoptotic on day 1, and lens fibers were degenerative at day 7, indicating the development of cataracts. Scattered foci of apoptosis in the neuroblastic layer of the retina on day 1, and rosettes were seen on day 7, suggestive of retinal dysplasia. CONCLUSION: Neonatal rats that received a threshold dose of PTX (4 mg/kg) at a critical period (0 days of age) developed cataracts and retinal dysplasia; however, the 2 mg/kg dose at 0 days of age and the 4 or 8 mg/kg dose at 14 days of age or older caused no ocular damage. Thus, the determination of the dose and timing of PTX treatment administered during the early developmental stage requires great care to avoid ocular toxicity.

Time-specific action of N-methyl-N-nitrosourea in the occurrence of retinal dysplasia and retinal degeneration in neonatal mice.

The morphologic response of neonatal mouse retina to the alkylating agent N-methyl-N-nitrosourea (MNU) was examined at different periods of retinal development. A dose of 60 mg/kg N-methyl-N-nitrosourea was injected intraperitoneally to neonatal C57BL mice at 0, 3, 5, 8, 11, 14, 17, and 20 days of age and to C3H mice at 0 days of age, and the retinas were examined sequentially. In the C57BL mice, MNU evoked a time-dependent occurrence of retinal dysplasia and retinal degeneration. With MNU treatment at day 0 and day 3 (the stage of retinal cell proliferation), retinal dysplasia characterized by the progressive disorganization of neuroblasts, which led to the formation of rosettes, was found in the outer neuroblastic/nuclear layer above the normal pigment epithelial cells during days 8-20, but decreased at day 50. The rosettes were surrounded by photoreceptor segments and Müller cell processes, and by photoreceptor nuclei. The MNU response was related to retinal differentiation; following MNU treatment at day 5 or 8 (the stage of retinal cell differentiation) the cells were much less sensitive (i.e. no retinal response was found). However, with MNU treatment at days 11, 14, 17, and 20 (after cellular differentiation), retinal degeneration characterized by selective photoreceptor apoptosis was seen. These results suggest that there is a critical period for the time of MNU administration in the development of mouse retinal lesions. In C3H (rd/rd) mice, MNU treatment at day 0 resulted in retinal degeneration with only slight rosette formation at the peripheral retina.