Nitric oxide synthase localization in cultured cerebrovascular endothelium during mitosis

Nitric oxide synthase (NOS) is present in cultured endothelial cells of cerebrovascular origin in a unique membrane-bound subcellular distribution. The enzyme can be detected by its ability to reduce nitro blue tetrazolium to an insoluble dense blue formazan precipitate. In resting cells, enzyme is located adjacent to the nuclear membrane in a single focus with very faint staining in the cytoplasm. During the various stages of cell division, however, NOS becomes redistributed in a pattern which appears similar to that of the Golgi complex. Enzyme is found concentrated near the spindle during early prophase and metaphase. During anaphase and telophase, NOS appears to also spread into the cytoplasm for redistribution into the daughter cells.