| Summary: | 碩士 === 國立臺灣大學 === 生化學研究所 === 87 === Numerous reports have documented the functions of hemoglobin in gas delivery in the lung and systemic microvasculature, but, to our knowledge, the effects of Hb on cell growth have not yet been reported. Here we show that: (1) Bovine methemoglobin (metHb) is capable of promoting the growth of several human cell lines, including nasal epithelial cell line, hepatoma cell line and normal fibroblast. (2) It has been postulated that nitric oxide is stabilized by hemoglobin that preserves its biological activity. We found that metHb preparations in which thiol groups of cysteine residues had been blocked with N-ethylmaleimide and the hemes blocked by cyanmet derivitization caused a decrease in activity of stimulating cell growth. (3) The effects of metHb alone or in different combinations with EGF and insulin on DNA synthesis were analyzed by [3H]-thymidine labeling and flow cytometry. In the presence of EGF or insulin, metHb stimulates DNA synthesis and induces hyperphosphorylation of retinoblastoma (Rb) tumor suppressor protein. These observations suggest that metHb promotes cell growth through delivering nitric oxide.
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