| Abstract: | Extracellular K+ enhances the chemotactic responsiveness and spontaneous movememt of rabbit peritoneal neutrophils but is not required for these functions. Other monovalent cations act the same; the rank order of their effectiveness is K+ = NH4 greater than Rb+ Cs+ greater than Li = Na. The K+ specific ionophore, valinomycin (10-7 M) inhances chemotaxis in the presence of K+ but not in its absence; another K+ specific ionophore, nigericin (10-7 M) inhibits chemotaxis in the absence of K+ but not in its presence. Ouabain (5 x 10-6 M) prevents the enhancing effects of K+ on chemotaxis. Removing the Na+ of the buffer and substituting it with K+, choline or glucose greatly enhances spontaneous motility but depresses chemotactic activity. One hypothesis suggested by the above results is that as a part of their action, chemotactic factors stimulate a net influx of K+ into the neutrophil; an alternative or additional hypothesis is that chemotactic factors stimulate a net efflux of Na+ from the neutrophil. |
