title: Passive potassium transport in LK sheep red cells. Effects of anti-L antibody and intracellular potassium.
abstract: The passive K influx in low K(LK) red blood cells of sheep saturates with increasing external K concentration, indicating that this mode of transport is mediated by membrane-associated sites. The passive K influx, iMLK, is inhibited by external Na. Isoimmune anti-L serum, known to stimulate active K transport in LK sheep red cells, inhibits iMLK about twofold. iMLK is affected by changes in intracellular K concentration, [K]i, in a complex fashion: increasing [K]i from near zero stimulates iMLK, while further increases in [K]i, above 3 mmol/liter cells, inhibit iMLK. The passive K influx is not mediated by K-K exchange diffusion. The effects of anti-L antibody and [K]i on passive cation transport are specific for K: neither factor affects passive Na transport. The common characteristics of passive and active K influx suggest that iMLK is mediated by inactive Na-K pump sites, and that the inability to translocate Na characterizes the inactive pumps. Anti-L antibody stimulates the K pump in reticulocytes of LK sheep. However, anti-L has no effect on iMLK in these cells, apparently because reticulocytes do not have the inactive pump sites which, in mature LK cells, are a consequence of the process of maturation of circulating LK cells. The results also indicate that anti-L alters the maximum velocity of both active and passive K fluxes by converting pumps sites from a form mediating passive K influx to an actively transporting form.
mesh_terms: D000818:Animals; D001665:Binding Sites; D001692:Biological Transport / Q000187:drug effects; D001693:Biological Transport, Active; D004912:Erythrocytes / Q000378:metabolism*; D006041:Goats; D007106:Immune Sera / Q000494:pharmacology; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000378:metabolism; D007700:Kinetics; D008951:MNSs Blood-Group System; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D012156:Reticulocytes / Q000378:metabolism; D012756:Sheep; D012964:Sodium / Q000378:metabolism
chemical_list: D007106:Immune Sera; D008951:MNSs Blood-Group System; D010042:Ouabain; D012964:Sodium; D011188:Potassium