Abstract
Passive calcium influx is one of the theories to explain the cathodal galvanotaxis of cells that utilize the electric field to guide their motion. When exposed to an electric field, the intracellular fluid becomes polarized, leading to positive charge accumulation on the cathodal side and negative charge accumulation on the anodal side. The negative charge on the anodal side attracts extracellular calcium ions, increasing the anodal calcium concentration, which is supposed to decrease the mobile properties of this side. Unfortunately, this model does not capture the Ca2+ dynamics after its presentation to the intracellular fluid. The ions cannot permanently accumulate on the anodal side because that would build a potential drop across the cytoplasm leading to an ionic current, which would carry positive ions (not only Ca2+) from the anodal to the cathodal part through the cytoplasm. If the cytoplasmic conductance for Ca2+ is low enough compared to the membrane conductance, the theory could correctly predict the actual behavior. If the ions move through the cytoplasm at a faster rate, compensating for the passive influx, this theory may fail. This paper contains a discussion of the regimes of validity for this theory.
Highlights
Cellular motility refers to the phenomena of cellular migration, which are involved in many biological processes
Galvanotaxis is a special class of the motility processes which is guided by external electric fields [3, 4], unlike the other common types of guided migration, such as chemotaxis, which is driven by chemical compound gradients [5] or phototaxis, which is driven by light intensity [6]
Starting with a stationary ionic distribution obtained for a cell with equal potentials on both ends, the external electric field was enabled and the simulation was run for 50 ms to obtain an ionic distribution which is close to the equilibrium, reached at t → ∞
Summary
Cellular motility refers to the phenomena of cellular migration, which are involved in many biological processes. Galvanotaxis based on receptor rearrangement requires some time to reach the stationary galvanotactic response, which is typically less than ten minutes [9] Another class of mechanisms highlights the importance of calcium ions for the cellular growth and motility processes [11]. They promote the capping of the barbed ends of actin filaments by gelsolin, preventing polymerization, and they cause myosin contraction, which is one of the factors responsible for the detachment of the rear side of the cell from the surface in a motile process [6, 10]. The galvanotactic response in such a mode can rise in less than 30 seconds [4]
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