Cellular target of weak magnetic fields: ionic conduction along actin filaments of microvilli

Abstract

Gartzke, Joachim, and Klaus Lange. Cellular target of weak magnetic fields: ionic conduction along actin filaments of microvilli. Am J Physiol Cell Physiol 283: C1333-C1346, 2002; 10.1152/ajpcell. 00167.2002.-The interaction of weak electromagnetic fields (EMF) with living cells is a most important but still unresolved biophysical problem. For this interaction, thermal and other types of noise appear to cause severe restrictions in the action of weak signals on relevant components of the cell. A recently presented general concept of regulation of ion and substrate pathways through microvilli provides a possible theoretical basis for the comprehension of physiological effects of even extremely low magnetic fields. The actin-based core of microfilaments in microvilli is proposed to represent a cellular interaction site for magnetic fields. Both the central role of F-actin in Ca 2ϩ signaling and its polyelectrolyte nature eliciting specific ion conduction properties render the microvillar actin filament bundle an ideal interaction site for magnetic and electric fields. Ion channels at the tip of microvilli are connected with the cytoplasm by a bundle of microfilaments forming a diffusion barrier system. Because of its polyelectrolyte nature, the microfilament core of microvilli allows Ca 2ϩ entry into the cytoplasm via nonlinear cable-like cation conduction through arrays of condensed ion clouds. The interaction of ion clouds with periodically applied EMFs and field-induced cation pumping through the cascade of potential barriers on the F-actin polyelectrolyte follows well-known physical principles of ion-magnetic field (MF) interaction and signal discrimination as described by the stochastic resonance and Brownian motor hypotheses. The proposed interaction mechanism is in accord with our present knowledge about Ca 2ϩ signaling as the biological main target of MFs and the postulated extreme sensitivity for coherent excitation by very low field energies within specific amplitude and frequency windows. Microvillar F-actin bundles shielded by a lipid membrane appear to function like electronic integration devices for signal-tonoise enhancement; the influence of coherent signals on cation transduction is amplified, whereas that of random noise is reduced. calcium signaling; cell differentiation; Brownian motor hypothesis; cyclotron resonance; hair cell; mechanoelectrical coupling; physiological effects MORE THAN A DECADE OF RESEARCH on field effects in biological systems has yielded rather compelling data for the involvement of the Ca 2ϩ signaling pathway as a primary and main target of magnetic fields (MFs). As first demonstrated by Liburdy and colleagues (52,53) and later on by a number of other authors, the Ca 2ϩ influx pathways of isolated or cultured cells are severely affected by rather low MF energies.The physiological relevance of this finding is high, because Ca 2ϩ represents the most important intracellular signal governing almost all physiological functions in differentiated cells. Most importantly, cytopla...

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“…The results obtained by Fukushima and coworkers [91] are consistent with those of Gartzke et al (2002), who pointed to the Ca 2+ signaling system as the primary cellular target of magnetic fields. Specifically, the ion-conducting actin filament bundle within microvilli was proposed as the cellular target for magnetic fields.…”

“…Specifically, the ion-conducting actin filament bundle within microvilli was proposed as the cellular target for magnetic fields. This target combines physiological relevance for Ca 2+ signaling with unusual electrical properties capable of explaining the effect of low-energy magnetic fields on biological systems [98]. This target was previously shown to exhibit nonlinear, cable-like cation conduction through arrays of condensed ion clouds.…”

“…This target was previously shown to exhibit nonlinear, cable-like cation conduction through arrays of condensed ion clouds. Stochastic resonance and/or the Brownian motor hypothesis were employed to explain how the interaction of ion clouds with periodically applied electromagnetic fields results in cation pumping through a cascade of potential barriers within polyelectrolytes [98]. The proposed interaction mechanism was in accord with the postulated extreme sensitivity for excitation by very low field energies within specific amplitude and frequency windows.…”

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“…Filaments present in microvilli may be involved in many of the biochemical and morphological changes observed following exposure of cells to SMF. The actin-based core of microfilaments in microvilli is proposed to act as a cellular interaction site for magnetic fields (17,18 ] i regulates numerous biological processes, including cytoskeletal reorganization (21), cell orientation (22), and migration (23). Re-arrangement of microtubules under the influence of SMF may also be responsible for cell orientation.…”

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“…Various models of explanation of interaction between MFs and Ca 2+ have been proposed, from physics viewpoint such as ion parametric resonance model by Lednev (Lednev, 1991) and ion interference model by Binhi (Binhi, 1997), but they do not cover the knowledge gap about the biochemical interaction site for MFs, in the cellular system. Gartzke and Lange supported that the ion-conducting actin filament bundle within microvilli, could play the role of the cellular target system for MF (Gartzke & Lange, 2002). The analytic description of the above mechanistic models does not fall into the aims of this paragraph.…”