thallium ions ( 2.5 x 10 ( -3 ) and 5 x 10 ( -3 ) mol/l ) in sodium- and potassium- free magnesium ringer solution caused a large increase in effluxes of all the cations examined ( k+ , rb+ and na+ ) both in presence and absence of gramicidin .
C0022023
ions
C0007447
cations