Oscillations and cyclic AMP‐induced changes of the K+ concentration in Dictyostelium discoideum

• Published in: The EMBO journal Vol. 4; no. 1; pp. 39 - 43
• Main Authors: Aeckerle, S., Wurster, B., Malchow, D.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 01-01-1985
• Subjects: Ammonia - metabolism; Biological and medical sciences; Calcium - metabolism; Cell physiology; Cyclic AMP - metabolism; Cyclic AMP - pharmacology; Dictyostelium - drug effects; Dictyostelium - metabolism; Fundamental and applied biological sciences. Psychology; Membrane and intracellular transports; Molecular and cellular biology; Potassium - metabolism; Dictyostelium discoideum; Cell culture; Protozoa; Monovalent cation; Regulation(control); Ion transport; AMP-3',5'; Concentration; Extracellular; Potassium
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1002/j.1460-2075.1985.tb02314.x

By means of a K+‐sensitive electrode, the extracellular K+ concentration was monitored in cell suspensions of Dictyostelium discoideum. In aggregative cells the attractant cyclic AMP induced a transient release of K+. The response was detectable within 6‐12 s and peaked at 30‐40 s. The apparent rate of release amounted to 7 X 10(8)K+ ions per cell per min. Adenosine and 5′ AMP, which are chemotactically inactive, did not elicit measurable K+ responses. The cyclic AMP‐induced release of K+ depended on the state of differentiation of the cells. In undifferentiated cells cyclic AMP did not cause a measurable K+ release, whereas folic acid, a potent attractant at this cell stage, induced a weak but significant K+ response. The cyclic AMP‐induced K+ release in aggregative cells was inhibited by K+‐channel blockers such as quinine and tetraethylammonium. In suspensions of differentiated cells free running oscillations of the extracellular K+ concentration were observed. K+ oscillations were related to cyclic AMP oscillations and oscillations of the light‐scattering properties of cells. Cells continuously released NH4+; however, cyclic AMP did not induce a measurable change of NH4+ release.