Calcium transport in inside-out membrane vesicles prepared from rabbit neutrophils.

Inside-out membrane vesicles capable in the presence of MgATP of accumulating calcium and containing Ca2+-ATPase activity have been prepared from rabbit neutrophils. The transport system has a Km for Ca2+ of 2.8 +/- 0.3 microM and a Vmax of 5.3 +/- 0.3 nmol/mg of protein . min and a Km for ATP of 0.35 +/- 0.13 mM and a Vmax of 5.8 +/- 0.3 nmol/mg protein . min. The Ca2+-activated ATPase system has a Km for Ca2+ of 0.2 +/- 0.05 microM and a Vmax of 4.0 +/- 0.5 nmol/mg protein . min, and a Km for ATP of 0.36 +/- 0.2 mM and a Vmax of 5.0 +/- 0.6 nmol/mg protein . min. It was also found that neither these inside-out vesicles nor the intact rabbit neutrophils contain a Na+/Ca2+ exchange mechanism.