Effect of Alternating Magnetic Field at Extremely Low
Frequency on Cells: Secretion of Insulin by Beta Cells
Wataru Ikeda, Shigehiro Hashimoto, Yuta Morioka, Yusuke Morita, Koichi Imoto,
Masahiko Yoshiura, Tomohiro Sahara, Kenichi Yamasaki, Hideo Kondo, Takatsugu Furukawa
Biomedical Engineering, Osaka Institute of Technology, Osaka, 535-8585, Japan
hasimoto@elc.oit.ac.jp
andHajime Otani, Hiroji Imamura, Toshiji Iwasaka
Cardiovascular Center, Kansai Medical University, Moriguchi, Japan
ABSTRUCTThe effect of alternating magnetic field atextremely low frequency on secretion of insulin
from beta cells has been investigated in vitro.
Beta cells from a hamster were exposed to theuniform magnetic field with the Helmholtz coil.
After
three
days
cultivation,
insulinconcentration in the medium was measured.
The experimental results show that secretionof insulin by beta cells tend to decrease by
exposure to alternating magnetic field.
Keywords: Bio-measurement, Magnetic field,
Extremely low frequency, Cell-culture, Insulin,
Beta cell, Helmholtz coil
1. INTRODUCTION
The effects of the magnetic field on a living
body were discussed in many previous studies.
Some epidemiological researches show possible
effects of the magnetic field on human health.
Electromagnetic effects are sometimes applied
to accelerate wound healing. Some animal
tests were also performed in the previous
studies. The effect of magnetic field on cells
had been measured in some previous studies[1-5]. Another experiments show that themolecules of collagen orient along the static
magnetic field.

Beta cells are included in the islets ofLangerhans in the pancreas and secrete
insulin to control the blood sugar levels.
In the present study, an experimental
equipment has been manufactured with theHelmholtz coil to generate uniform alternating
magnetic field at extremely low frequency, andthe effect of alternating magnetic field atextremely low frequency on secretion of insulin
from beta cells has been investigated in vitro..
2. METHODS
Helmholtz coil
An alternating magnetic field is generated
around a coil with alternating electric current.
To generate uniform magnetic field, Helmholtz
coil was applied. The Helmholtz coil consistsof two circular coils of which both radius andturns are equal to each other.
In theHelmholtz coil, two coils are located in theparallel position with the common axis. The
distance between two coils is equal to theradius of the coil.
The magnetic field generated between two coils
is quasi-uniform, and the magnetic flux
density between them is approximately
constant [2].

(b)

(a)

Fig. 1: Helmholtz coil: (a) front view, (b) sideview.
Oscilloscope

Oscillator

Magnetic shieldHelmholtz coil
Voltage to current converter

Current value calculated frommeasurement voltage （mA）

Fig. 3: Voltage to current converter.

3.60
3.40
3.20
3.00
2.80
2.60
2.40
0

500

1,000

1,500

2,000

Load resistance（Ω）

Fig. 2: Experimental system.

Fig. 4: Relation between current and load resistance.

A uniform alternating magnetic field (50 Hz,
0.01 mT) was generated with the Helmholtz
coil manufactured with radius of 80 mm (Fig.
1). The plate with 24 wells was placed in themagnetic field so that the culture plane of thedish is parallel to the magnetic field.

Through the converter, the output electric
current is controlled with the input voltage(Fig. 3). The current in the coil is able to be
kept constant independent of load resistance (<800 Ohm) of the coil (Fig. 4).

The Helmholtz coil was enclosed with theflexible sheet of metal to shield theexperimental space from the surrounding
magnetic field (Fig. 2). In the control group,
the culture plate was also enclosed with themetal sheet without the coil to be shieldedfrom magnet fields generated by surroundings.

The input voltage generated with the oscillator
is converted into the electric current, whichflows in the Helmholtz coil.
In theexperiment, both the magnetic flux densityand frequency were controlled with theoscillator. The wave-forms of input voltage
and output current are measured with an
oscilloscope.
The generated magnetic flux
density is measured with the gauss-meter.

Magnetic field strength（μT）

100μm

12.00010.000
8.000
6.000
4.000
2.000
0.000
0

200

400

600

800

600

800

Cell culture
Pancreatic beta cells from a Syrian hamster(HIT-T15) were cultured in the F-12K medium(Sodium bicarbonate, L-glutamine) withdialyzed horse serum in 10 percent and fetal
bovine serum in 2.5 percent at 37 degrees
Celsius (Fig. 5). After exfoliation from a dishwith trypsin solution of 2.5 percent andcentrifugation at 100 G for one minute, thecells were seeded with density of 32 cells per
micro-liter into wells. Two plates of 24 wells
were used for cultivation: one is for exposure to
the magnetic field, and the other is for control.
The cells were cultivated in the uniform
magnetic field for three days. The results
were evaluated about multiplication rate ofcells, and secretion of insulin.

12.00010.000
8.000
6.000
4.000
2.000
0.000
0

200

400
Time（s）

Fig. 6: Magnetic field intensity; at middle
part, upper; at corner part, lower.
0.4

AbsorbanceFig. 5: Beta cells.

Magnetic field strength（μT）

Time（s）

0.3
0.2
0.1
0

The population of cells in each well wascounted with a hemocytometer after tests.
After
three
days
cultivation,
insulinconcentration in the medium of each well wasmeasured.
After reaction with antibody,insulin concentration was quantified withextinction intensity at wavelength of 492 nm.
Data were compared between cells exposed tothe magnetic field and those shielded frommagnetic field (control).
3. RESULTS AND DISCUSSION
Magnetic field was kept constant regardless ofthe position in Helmholtz coil (Fig. 6).

10

100

1000

10000

Insulin Concentration (pg/ml)

Fig. 7: Calibration for insulin concentration.

The population of cells increases exponentiallywith time. Table 1 shows cell population
calculated from the cell density in each wellafter the test. The proliferation rate in themagnetic field was similar to that in control
condition.

Exposure
Cell

A
8

B
9

C
11

D
13

Mean
9.8

Some previous studies show that the magnetic
field attenuates insulin secretion from theinsulinoma [8].
The magnetic field has
possibility for noninvasive treatments fordiabetes.

Control
Cell

E
6

F
7

G H
10 14

Mean
9.3

4. CONCLUSION

Insulin Concentration (ng/ml)

Table 1: Cell population after test; x104

3.5

The experimental study shows that secretionof insulin by beta cells tends to decrease by
exposure to alternating magnetic field.

3

5. ACKNOWLEDGMENT

2.5
2
1.5
1
0.5

This work was supported in part by aGrant-in-Aid for Scientific Research andAcademic Frontier from the Japanese Ministryof Education, Culture, Sports, Science andTechnology.

0
6. REFERENCES

Fig. 8: Insulin concentration; exposure(left), control (right).

Figure 7 shows the calibration curve forinsulin concentration.
Figure 8 showsconcentration of insulin after the test. Data
show the mean value in four wells each: theexposure group and the control group. The
mean value of insulin concentration in themedium exposed to the magnetic field was
lower than that in control.
The intensity of surrounding magnetic fields
sufficiently decreased with the flexible sheet ofmetal.
Experimental systems had been designed to
improve magnetic conditions to study the effectof magnetic field on cell culture [6, 7]. The
Helmholtz coil is effective to generate theparallel magnetic field.
The uniform
alternating magnetic field was controlled in
the present experimental device with theHelmholtz coil and with the flexible sheet of
micro-grain metal.
The intensity level of
0.0005 mT occurs in the atmosphere of daily
urban life.

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