Cavill Ivor
University College of Wales, Cardiff, Wales, UK.
Nephrol Dial Transplant. 2002;17 Suppl 5:19-23. doi: 10.1093/ndt/17.suppl_5.19.
Our knowledge of erythropoiesis and iron in renal disease is limited. The accepted view of the control of erythropoiesis was founded on observations made in a variety of disorders, but the control mechanism in healthy individuals may not be quite the same. Evidence suggests that mechanisms other than erythropoietic stimulation may play a role in increased red blood cell production. Measuring erythropoiesis is complex. The quantitative reticulocyte count is probably the closest practical assessment of erythropoietic activity we can achieve, yet there is very little correlation between circulating erythropoietin level and reticulocyte count in normal and near normal subjects. Oxygen transport in humans depends entirely upon iron. In renal disease, the failure of the erythropoietin positive feedback mechanism can be readily and directly remedied; recombinant human erythropoietin therapy can replace the missing erythropoietin, but this will be negated if iron supply to the erythroid marrow falls short of demand. Measurement of iron stores is also complex. The use of serum ferritin concentration as a direct quantitative estimate of iron in the stores is not advisable, and in practice we have not found the transferrin receptor assay to be useful in identifying patients who require iron therapy. Use of percentage hypochromia as a measure of iron deficiency is complicated by the fact that hypochromic cells are not exclusively a consequence of functional iron deficiency. There are clearly lessons still to be learned in this field and there is much that we do not yet understand about the control of erythropoiesis and iron metabolism in humans.
我们对肾脏疾病中红细胞生成和铁的了解有限。关于红细胞生成控制的公认观点是基于对多种疾病的观察得出的，但健康个体中的控制机制可能并不完全相同。有证据表明，除了红细胞生成刺激之外的机制可能在红细胞生成增加中起作用。测量红细胞生成很复杂。网织红细胞定量计数可能是我们能够实现的对红细胞生成活性最接近实际的评估，然而在正常和接近正常的受试者中，循环促红细胞生成素水平与网织红细胞计数之间几乎没有相关性。人类的氧气运输完全依赖于铁。在肾脏疾病中，促红细胞生成素阳性反馈机制的失效可以很容易且直接地得到纠正；重组人促红细胞生成素疗法可以替代缺失的促红细胞生成素，但如果红系骨髓的铁供应不足，这一作用将被抵消。铁储存的测量也很复杂。使用血清铁蛋白浓度作为铁储存量的直接定量估计并不可取，而且在实践中我们发现转铁蛋白受体检测对于识别需要铁治疗的患者并无帮助。使用低色素百分比作为缺铁的衡量指标很复杂，因为低色素细胞并不完全是功能性缺铁的结果。在这个领域显然仍有许多教训需要吸取，而且我们对人类红细胞生成和铁代谢的控制还有很多不了解的地方。
