Granule enzymes of human and rabbit polymorphonuclear leukocytes: an investigation of enzyme solubility

Granules were isolated from both human and rabbit polymorphonuclear leukocytes (PMNs), and the quantity and solubility of certain granule enzymes compared. Lysozyme and alpha-mannosidase were found to be the most soluble enzymes in the granules of both species and could be released by lysis with 0.1% (v/v) Triton X-100. Alkaline phosphatase was also released by this lytic procedure, but its release required higher concentrations of Triton. The main difference between the species was found in the less-soluble enzymes that were retained as an insoluble complex after lysis by Triton X-100. Both myeloperoxidase and the neutral proteinase activity of rabbit PMNs were found to be highly insoluble, requiring 0.6 M sodium chloride for their extraction from this complex. The corresponding enzymes from human PMNs were more soluble, 0.15 M sodium chloride releasing the majority of the neutral proteinase activity. In addition, the insolubility of the rabbit neutral proteinase activity seemed to prevent its release from PMNs stimulated to degranulate in vitro by treatment with the calcium ionophore, A23187. Since rabbit PMNs were also shown to contain significantly less neutral proteinase activity than human PMNs, it would seem that the rabbit is a poor model for the study of PMN-mediated tissue injury in man.