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 �M and veratridine at 100 �M. Both the channel-blockers amiloride (1 mM) and saxitoxin (1 �M), 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.