[Nitroblue tetrazolium reduction by human blood neutrophils. I. The influence of pH]

Activity of blood neutrophils of 14 healthy volunteers (8 women, 6 men, aged from 21 to 37 years) was investigated in the Nitroblue Tetrazolium (NBT) reduction reaction at pH 7.0, 7.3, and 7.6. The dependence of the percentage of NBT-positive neutrophils on the reaction time was described by a kinetic equation with constants k1 and k2, characterizing, accordingly, speeds of NBT absorption and reduction by neutrophils. A strong positive correlation (r = 0.99; P < 0.0001), was found between k1 and k2, which pointed to dependence of the speed of NBT restoring by neutrophils on the speed of its entry to the cell. Both the constants and speeds of successive process stages have maximum values at pH 7.3 (corresponding to physiological value of blood pH), and decrease at medium acidification or alkalization. The k1/k2 ratio does not depend on the time (0-6 h) or pH (7.0-7.6) of blood incubation before the reaction. The most active neutrophils (potential pH agocytes) have a lesser membrane permeability than do neutrophils of another class, and their activity more increases at medium acidification in vitro and, probably, in vivo. The activation of neutrophils leads to an increase in medium pH that alongside with an increase in the number of active potential phagocytes, evidently has a physiological meaning.