The participation of calcium, adenosine triphosphate and adenosine triphosphatase in the extrusion of the granule proteins from the polymorphonuclear leucocyte

Abstract

The extrusion of the granule proteins from the leukocyte can be induced by vitamin A if calcium is present. The process is stimulated by ATP. The extrusion from the leucocidin-treated leukocyte can take place in potassium chloride, sodium chloride or sucrose solution. It is stimulated by low but inhibited by high calcium or ATP concentrations. The optimum ATP concentration is dependent on the calcium concentration. Magnesium is inhibitory. When extrusion is stimulated with [P32]APT 90% of the radioactivity can be recovered and all is in the acid-soluble fraction. The specific radioactivity of the phos-pholipids is not increased. The release of enzymes from the isolated granules is not stimulated by calcium or ATP. Some properties of the adenosine triphosphatase of the granules are described. It is suggested that, though both calcium and ATP must be present for the adherence of the granules to the cell surface membrane, they must both be removed for the extrusion of protein to occur. A mechanism involving hydrolysis of ATP by the adenosine triphosphatase of the granules is described. The fusion of the membranes of the granule and cell surface may be facilitated by decreased cross-linking in the membranes after the elimination of calcium and ATP. The participation of phospholipids in the extrusion process is discussed.