Search for ion-cyclotron resonance in an Na(+)-transport system

Colonic tissue from the turtle (Pseudemys scripta) was exposed in a Ussing chamber to simultaneously applied static and time-varying magnetic fields. Transepithelial differences of potential were monitored as frequency of the AC field was varied continuously or in discrete steps from 3 to 770 Hz. Density of the DC field was varied from 10 to 220 microT and that of the AC field from 1 to 20 microT. Short-circuit currents through tissue were monitored for changes that might have been observed under ion-cyclotron resonance (ICR) conditions for each of several ions: H+, Li+, Na+, K+, Ca2+, and Cl-. No discernible changes of transepithelial current were observed. The negative findings are discussed in relation to positive and negative findings that have appeared in the literature.