Modeling of the effect of modulated electromagnetic radiation on animal cells

Gapeev AB, Chemeris NK,

Biofizika 45(2):299-312, 2000

[Article in Russian] Frequency-dependent modifications of intracellular free calcium concentration ([Ca²⁺]i) in neutrophils exposures to modulated extremely high frequency electromagnetic radiation were analyzed using a special mathematical model for [Ca²⁺]i oscillations. The model took into account the activation of Ca²⁺ influx into the cell by cytosolic Ca2+ and Ca(²⁺)-induced Ca²⁺ release from intracellular stores.

The calcium channels of plasma membrane were chosen as a target for the influence of harmonic signal and additive noise in the model. The model simulation showed that in response to modulating signal, the rise in [Ca²⁺]i, has frequency dependence and phase dependence in relation to the moment of chemical stimulation. The phase-frequency dependence of the effect was observed at a certain sequence of delivery of chemical stimulus and modulating signal to the cell.

At intensities of modulating signals exceeding the threshold, a rise in [Ca²⁺]i, reaching a level of more than 50% of the initial level, was observed at a frequency of about 1 Hz and in the phase range of 0.3-2.5 radians.

The effect was found only at high intensities of chemical stimulus. The additive noise introduced into the system modified qualitatively and quantitatively the phase-frequency characteristics of the cell response to the modulating signal. An increase in noise intensity resulted in a displacement of the average frequency of the band of rise in [Ca²⁺]i, and then the emergence of a set of bands with a greater Q-factors.

The analysis of dynamics of the nonlinear system in terms of the stability theory showed that, as the intensity of chemical stimulus increases, the system transits by means of a series of bifurcations from regular driving to chaotic, and then to oscillations, induced by a modulating harmonic signal. The boundary of the transition of oscillations from chaotic to induced ones corresponds to a specific "threshold" of the intensity of chemical stimulus for the significant rise in [Ca²⁺]i in response to the modulating signal.

The results of the model analysis are in good correspondence with the experimental data obtained earlier, namely, with the effects of modulated extremely high-frequency electromagnetic radiation on neutrophils, which were observed only in the presence of Ca²⁺ in extracellular medium and at high concentrations of calcium ionophore A23187.

Thus, as the characteristic frequency of the quasi-periodic process of calcium signalling in the cell coincides with the frequency of external field, a narrow-band rise in [Ca²⁺]i is observed, which can result in a modification of the functional activity of the cell.