EFFECTS OF STATIC MAGNETIC-FIELD ON SPECIFIC ADENOSINE-5'-TRIPHOSPHATASE ACTIVITIES AND BIOELECTRICAL AND BIOMECHANICAL PROPERTIES IN THE RAT DIAPHRAGM MUSCLE

In this study, we aimed to clarify the effects of chronically applied static magnetic field (200 Gauss) on specific ATPase activities and bi oelectrical and biomechanical responses in the isolated rat diaphragm muscle. The mean activities of Na+-K+ ATPase and Ca2+ ATPase determine d from the diaphragm homogenates were significantly higher in the magn etic field exposed group (n = 20), but that of Mg2+ ATPase was nonsign ificantly lower compared to the control group (n = 13). Resting membra ne potential, amplitude of muscle action potential, and overshoot valu es (mean +/- SE) in the control group were found to be -76.5 +/- 0.6, 100 +/- 0.8, and 23.5 +/- 0.6 mV, respectively; these values were dete rmined to be -72.8 +/- 0.4, 90.3 +/- 0.5, and 17.2 +/- 0.4 mV in the m agnetic field-exposed group, respectively. The latency was determined to increase in the experimental group, and all the above-mentioned bio electrical differences between the groups were significant statistical ly. Force of muscle twitch was found to decrease significantly in the magnetic field-exposed group, and this finding was attributed to the a ugmenting effect of magnetic field on Ca2+ ATPase activity. These resu lts suggest that magnetic field exposure changes specific ATPase activ ities and, thence, bioelectrical and biomechanical properties in the r at diaphragm muscle. (C) 1995 Wiley-Liss, Inc.