The incorporation of radioactive phosphorus in the leucocyte during the extrusion of protein induced by staphylococcal leucocidin

Abstract

Incubation with leucocidin stimulates the incorporation of P32 into the adenosine tri- and di-phosphate and guanosine tri- and di-phosphate of the leucocyte. Incubation with leucocidin does not increase the permeability of the leucocyte to ortho-phosphate and in the presence of P32 does not increase the radioactivity of the intracellular orthophosphate. In the presence of fluoride, iodo-acetate or arsenate the incorporation of P32 into the lipids and nucleo-tides of the leucocidin-treated leucocyte is partially inhibited. The extrusion of [beta]-glucuronidase is not affected under these conditions. Omission of calcium from the medium stimulates the incorporation of p32 into the lipids of the leucocidin-treated leucocyte and reduces the amount of incorporation into the nucleotides. Either component of leucocidin adsorbed on the leucocyte can be neutralized by antibody. Addition of antibody to the leucocidin-treated leucocyte does not inhibit the incorporation of p32 into the nucleotides. Treatment with leucocidin decreases the rate of loss of radioactivity from the nucleotides of leucocytes labelled with p32 and suspended in a medium of low specific radioactivity. Treatment with leucocidin reduces the amount of [Cl4]-adenine incorporated into adenosine triphosphate and the amount of [C14]acetate incorporated into the lipids of the cell. It is suggested that the stimulation of incorporation of P32 in the leucocidin-treated leucocyte does not result from an increased rate of turnover of any phosphorus compound of the cell but can result from direct utilization at the cell surface of the external orthophosphate.