Use of Ion-Channel Modulating Agents to Study Cyanobacterial Na(+) - K(+) Fluxes

Here we describe an experimental design aimed to investigate changes in total cellular levels of Na(+) and K(+) ions in cultures of freshwater filamentous cyanobacteria. Ion concentrations were measured in whole cells by flame photometry. Cellular Na(+) levels increased exponentially with rising alkalinity, with K(+) levels being maximal for optimal growth pH (~8). At standardized pH conditions, the increase in cellular Na(+), as induced by NaCl at 10 mM, was coupled by the two sodium channel-modulating agents lidocaine hydrochloride at 1 μM and veratridine at 100 μM. Both the channel-blockers amiloride (1 mM) and saxitoxin (1 μM), decreased cell-bound Na(+) and K(+) levels. Results presented demonstrate the robustness of well-defined channel blockers and channel-activators in the study of cyanobacterial Na(+)- K(+) fluxes.