(581c) Dielectrophoresis Shows That Regular Potassium Transport Controls the Circadian Electrophysiological Rhythm in Human Red Blood Cells

The standard model of biological rhythmic behaviour (also called “circadian”, from the Latin for “around a day”) is one based on gene expression cycles; several genes are activated and inactivated in a near-24-hour pattern in nucleated cells, following a well-characterised mechanism. However, this model was challenged when circadian rhythms in PRX activity were observed in isolated mammalian red blood cells (RBCs), which lack nuclei. This suggested the presence of a non-genetic mechanism which operates in RBCs. In order to investigate this mechanism, we employed a combination of approaches to scrutinize the causes and consequences of timekeeping in RBCs. These studies indicated highly rhythmic, sinusoidal rhythms in the membrane conductance and cytoplasmic conductivity of isolated RBCs. Using a combination of approaches including dielectrophoresis and ICP-MS, we have identified rhythms in both K⁺-flux and intracellular K⁺. We also found that we could speed up, slow down or completely abolish the rhythm in DEP properties by using pharmacological intervention and ion replacement. These results indicate that K⁺-transport underlies the circadian rhythms of RBC membrane physiology and suggest that K⁺-transport may contribute to the determination of circadian period in isolated RBCs.