Haaskjold E, Refsum H, Refsum S B, Bjerknes R
Department of Ophthalmology, University of Oslo, Rikshospitalet, Norway.
APMIS. 1992 Dec;100(12):1123-8. doi: 10.1111/j.1699-0463.1992.tb04049.x.
In the rat corneal epithelium the mitotic rate (MR) is almost equal throughout the epithelium in the morning (Haaskjold et al. 1988). The labelling index (LI) shows a marked reduction in the central cornea, which could suggest a lack of uptake of tritiated thymidine via the salvage pathway (Haaskjold et al. 1989). In the present study we have used [3H]deoxycytidine, and [3H]thymidine after prior treatment with a methotrexate regimen to elucidate this discrepancy. Deoxycytidine is incorporated into DNA independent of thymidine kinase, while methotrexate, which depletes the cells of reduced folates, makes the cells completely dependent on the salvage pathway. With both techniques the same pattern of labelling was observed, confirming that in the morning the ratio between the MR and the LI differs throughout the cornea. Based on previous observations, an analysis of the MR/LI ratio during 24 h was performed, showing that these parameters were strongly correlated. This suggests that there may be different circadian variations in the cell proliferation parameters throughout the corneal epithelium. The methotrexate regimen may be a useful tool to investigate the salvage pathway.
在大鼠角膜上皮中，有丝分裂率（MR）在早晨时在整个上皮中几乎相等（哈斯乔尔德等人，1988年）。标记指数（LI）显示中央角膜有明显降低，这可能表明通过补救途径摄取氚标记胸腺嘧啶核苷存在缺陷（哈斯乔尔德等人，1989年）。在本研究中，我们使用了[3H]脱氧胞苷，以及在用甲氨蝶呤方案预处理后使用[3H]胸腺嘧啶核苷，以阐明这种差异。脱氧胞苷可独立于胸腺嘧啶激酶掺入DNA，而耗尽细胞内还原型叶酸的甲氨蝶呤使细胞完全依赖补救途径。使用这两种技术观察到相同的标记模式，证实早晨时整个角膜中MR与LI的比值不同。基于先前的观察结果，对24小时内的MR/LI比值进行了分析，结果表明这些参数密切相关。这表明整个角膜上皮的细胞增殖参数可能存在不同的昼夜变化。甲氨蝶呤方案可能是研究补救途径的有用工具。
