ATP-activated Ca 2+-permeable channels in rat peritoneal macrophages

The patch-clamp technique was used to study mechanisms of ATP-induced Ca 2+influx in rat peritoneal macrophages. The experiments on whole-cell and patch membranes have shown that extracellular ATP activates channels permeable to di- and monovalent inorganic cations. Ratios of unitary channel conductances in 105 mM Ca 2+, Sr 2+, Mn 2+, Ba 2+and normal sodium solutions were 1.0, 0.95, 0.75, 0.55 and 0.85, respectively. The channels could open in the presence of non-hydrolyzable GTP analogues in artificial intracellular solution. The data are consistent with the hypothesis that a GTP-binding protein is involved in receptor-to-channel coupling.