AN UPPER LIMIT FOR THE EFFECT OF LOW-FREQUENCY MAGNETIC-FIELDS ON ATP-SENSITIVE POTASSIUM CHANNELS

Currents have been recorded for ATP-sensitive potassium channels in ex cised patches of membranes from an insulin secreting cell line, CRI-G1 . The multi-channel records have been analyzed to reveal the single-ch annel conductance, the frequency and duration of bursts and the freque ncy of flickers (with periods between 0.5 and 5 ms). Control records i n the absence of applied magnetic fields are similar to those reported by others. Patches have been exposed to parallel static and low frequ ency magnetic fields including a combination satisfying the 'cyclotron resonance' condition. The fields were applied for 30 s periods interl eaved with 30 s controls. No significant differences in channel proper ties were observed between the control and field exposed periods. The largest change in position of the peak of the distribution of opening and closing transitions was 3%.