Model analysis of nonlinear modification of neutrophil calcium homeostasis under the influence of modulated electromagnetic radiation of extremely high frequencies.

The problem of resonance effects of electromagnetic radiation (EMR) on biological objects remained unsolved till now. Previously we demonstrated that low-intensity amplitude-modulated EMR of extremely high frequencies (EHF) modified the activity of mouse neutrophils in the synergistic reaction of calcium ionophore A23187 and phorbol ester PMA. The EHF EMR influence on the neutrophils was significant at the carrier frequencies of radiation within a narrow range of 41.8-42.05 GHz and at the modulation frequency of 1 Hz. The purpose of the work was the analysis of frequency-dependent modification of intracellular free calcium concentration ([Ca(2+)](i)) by modulated EHF EMR on the basis of a special model for [Ca(2+)](i) oscillations in the neutrophils. The calcium channels of plasma membrane were chosen as the action target of external modulation in the model. The computer simulation demonstrated the rise in [Ca(2+)](i) at the influence of the external field with a threshold dependence on the modulation amplitude. The effect depended heavily on a sequence of delivery of the chemical and electromagnetic stimuli. The narrow-band rise in [Ca(2+)](i) had a phase-frequency dependence. With the modulation amplitudes exceeding the threshold value, the rise in [Ca(2+)](i) of more than 50% of the initial level was observed at the frequency of about 1 Hz and in the phase range of 0.3-2.5 radians. The results of the model analysis are in good correspondence with the experimental data obtained before, namely, with the resonance modification of the neutrophil activity at the modulation frequency of 1 Hz and with the presence of the effect only at high concentrations of calcium ionophore.