Division of labor among the many types of cells found in metazoans is commonly observed and is accepted as one of the advantages conferred by multicellularity. Yet the function in which one cell type specializes is apt to be expressed, but to a lesser degree, in virtually all cell types. Thus, muscle cells, having specialized in movement, contain huge amounts of actin and myosin and the associated regulatory proteins of the contractile apparatus, while other cell types contain less of these proteins, commensurate with their more modest needs for movement. Indeed modern methods for amplification of DNA have been used to show that genes usually thought to be expressed only in specialized tissues are, in fact, transcribed, spliced, and polyadenylated, at low baseline rates, in all tissues examined (1). This line of reasoning leads to the expectation that membrane-associated and superoxide-producing NAD (P) H oxidases, which are abundant in phagocytic cells capable of mounting a respiratory burst (2-6), should also be found to a lesser degree in other cell types. Large fluxes of 0,) such as those associated with the respiratory bursts of eosinophils, macrophages, monocytes, and neutrophils, are easily detected. Not so the much smaller amounts of 0, which might be made at the surface of other cell types, due to both univalent NAD (P) H oxidases and to autoxidation of electron-carrying components. Amplification, such as that provided by O,-initiated free radical chain reactions (7), might allow detection of small fluxes of 0, _ Vanadate initiates and catalyzes a free radical chain oxidation of dihydropyridines such as NAD (P) H, or of NMNH, and this process provides the amplification needed to detect low lev-