Alkaline phosphatase as a marker of maturity in human neutrophils. Studies in normals dosed with aetiocholanolone and prednisolone.

Changes in the level of neutrophil alkaline phosphatase (NAP) in a population of peripheral blood neutrophils were determined in healthy subjects dosed with either aetiocholanolone (Aetio, 4 mg/m2 im) or prednisolone sodium succinate (Pred, 30 mg/m2 iv). Before dosing the mean NAP score, as measured by a modified Gomori azo-dye method, was 109 and 118 in the Aetio and Pred groups, respectively. Fifteen hours after injection the NAP score in the Aetio group had risen to 187 concomitant with the appearance of large numbers of juvenile (band) and mature neutrophils. Twenty-four hours after dosing, the NAP score increased to 213 with still further concentrations of juvenile cells, while the numbers of mature neutrophils returned to approximately baseline values. Five hours after injection, in subjects given Pred, the NAP score had fallen to 108 concomitant with a marked increase in the numbers of mature neutrophils. These data in normals dosed with either Aetio or Pred appear to substantiate a 'first-in, first-out' cellular progression with initial release of the oldest of the mature bone marrow reserve neutrophils containing less (relative to juvenile forms) NAP activity. These data also indicate that NAP activity is inversely related to cellular age and may support previous findings in the rat that enzyme levels are higher in bone marrow relative to peripheral blood.