Reversal of Na+-dependent glycine transport in sheep reticulocyte membrane vesicles.

Inside-out membrane vesicles have been prepared from sheep reticulocytes. With these vesicles, Na+-dependent glycine uptake and net accumulation have been demonstrated to occur in reverse, i.e., from extravesicular (normal cytoplasmic) to intravesicular (normal extravesicular) surface. Uptake and accumulation are inhibited by energization of the sodium pump by ATP whereby the Na+ electrochemical gradient is dissipated. Glycine-dependent Na+ uptake was also observed, providing evidence that Na+-dependent glycine influx into these vesicles, equivalent to normal efflux, is characterized by Na+-glycine co-transport.