Exploring Cellular Water Dynamics associated with Potassium Ion Changes Using Magnetic Resonance Imaging

Potassium ions play a critical role in modulating cellular physiology, but their direct effects on water dynamics have not been fully explored. Here, we investigated how elevated potassium ion concentrations ([K⁺]) alter intracellular and extracellular water pools in comparison to hypoosmotic stress, using T2 and magnetization transfer (MT) parameters in a close-packed T-lymphocyte cell pellet model. Our findings reveal that the T2 increase primarily reflects an increase in intracellular free water concentration rather than a mere expansion of cell volume. Notably, [K⁺] elevation produced distinct cell swelling profiles and a smaller relative rise in free water at comparable volumetric changes compared to hypoosmotic stress, highlighting more complex mechanisms than straightforward osmotic effects. While T2 proved sensitive to shifts in intracellular water content, the bound pool increased linearly with cell volume expansion. These results underscore that [K⁺]-driven cell swelling diverges functionally from osmotic- driven cell swelling and demonstrate the viability of MRI-based approaches for probing K⁺-dependent cellular events.