[Effects of power frequency magnetic field on Ca2+ transport of skeletal muscle sarcoplasmic reticulum vesicles]

Abstract

Objective: To investigate the effects of power frequency magnetic field on the Ca2+ transport dynamics of isolated sarcoplasmic reticulum vesicles.

Methods: The assays of Ca2+ uptake time course and the Ca2+-ATPase activity of sarcoplasmic reticulum vesicles were investigated by using dynamic mode of spectrometry with a Ca2+ dye; Ca2+ release channel activation was examined by 3H-ryanodine binding and Ca2+ release assays; membrane fluidity of sarcoplasmic reticulum vesicles was examined by fluorescence polarization, without or with exposure to the vesicles at a 0.4 mT, 50 Hz sinusoidal magnetic field.

Results: 0.4 mT, 50 Hz sinusoidal magnetic field exposure caused about a 16% decline of the initial Ca2+ uptake rate from a (29.18 +/- 3.90) pmol.mg(-1).s(-1) to a (24.60 +/- 3.81) pmol.mg(-1).s(-1) and a 26% decline of the Ca2+-ATPase activity from (0.93 +/- 0.05) micromol.mg(-1).min(-1) to (0.69 +/- 0.07) micromol.mg(-1).min(-1) of sarcoplasmic reticulum vesicles, whereas caused a 15% increase of the initial Ca2+ release rate from (4.83 +/- 0.82) pmol.mg(-1).s(-1) to (5.65 +/- 0.43) pmol.mg(-1).s(-1) and a 5% increase in 3H-ryanodine binding to the receptor from (1.10 +/- 0.12) pmol/mg to (1.16 +/- 0.13) pmol/mg, respectively.

Conclusion: The decline of Ca2+-ATPase activity and the increase of Ca2+ release channel activity should result in a down-regulation of Ca2+ dynamic uptake and an up-regulation of Ca2+ release induced by exposing the sarcoplasmic reticulum to a 0.4 mT, 50 Hz power frequency magnetic field.