Medical/biological study (experimental study)

Green tea catechins protect rats from microwave-induced oxidative damage to heart tissue med./bio.

By: Kim MJ, Rhee SJ

Published in: J Med Food 2004; 7 (3): 299-304

Aim of study (acc. to author)

To study the effects of green tea catechins (antioxidants) on oxidative damage in the heart tissue of microwave exposed rats.

Background/further details

The exposed rats received one of three diets: 1) catechin-free, 2) 0.25% catechin, or 3) 0.5% catechin. Each group consisted of ten rats. Rats were sacrificed 6 days after microwave irradiation

Endpoint

effects on the cardiovascular system: oxidative damage and antioxidative defense system in the heart

Exposure

- 2.45 GHz
- microwaves
- CW continuous wave

Exposure	Parameters
Exposure 1: 2.45 GHz Modulation type: CW Exposure duration: continuous for 15 min.	power density: 40 mW/cm² (at a distance of 35 cm) SAR: 9.2 W/kg average over mass (whole body)

General information

Microwave exposed animals were divided into three groups: i) catechin-free diet ii) 0.25 % catechin dietary supplement iii) 0.5 % catechin dietary supplement

Exposure 1

Main characteristics

Frequency	2.45 GHz
Type	electromagnetic field
Exposure duration	continuous for 15 min.

Modulation

Modulation type	CW

Exposure setup

Exposure source	modified household microwave oven

Parameters

Measurand	Value	Type	Method	Mass	Remarks
power density	40 mW/cm²	-	measured	-	at a distance of 35 cm
SAR	9.2 W/kg	average over mass	measured	whole body	-

Exposed system:

Methods Endpoint/measurement parameters/methodology

effects on the cardiovascular system: oxidative damage and antioxidative defense system (cytochrome P450 level; enzyme activities of NADPH-cytochrome P450 reductase, of superoxide dismutase and glutathione peroxidase; content of superoxide radical, lipofuscin and carbonyl groups (as index for oxidized proteins); lipid peroxidation (malondialdehyde content; thiobarbituric acid method))

Investigated system:

heart microsomes

Investigated organ system:

cardiovascular system

Time of investigation:

after exposure

Main outcome of study (acc. to author)

Cytochrome P450 levels in the catechin-free microwave exposed group were increased by 85% compared with the control group. However, they were 11% and 14% lower in the "microwave + 0.25 % catechin" and "microwave + 0.5 % catechin" groups than in the catechin-free group.
NADPH-cytochrome P450 reductase enzyme activity in the catechin free group was increased by 29%, compared to the control group, but it was significantly less in the "microwave + 0.25 % catechin" and "microwave + 0.5 % catechin" groups.
Superoxide dismutase activity in the catechin-free group was decreased by 34%, compared with the normal group, but in the "microwave + 0.25 % catechin" and "microwave + 0.5 % catechin" groups it was 19% and 25% higher compared to the catechin-free group. The enzyme activity of glutathione peroxidase in the catechin-free microwave exposed group was decreased by 28% but remained near normal value with catechin supplements.
Superoxide radical concentration in the catechin-free microwave exposed group was increased by 35% compared with the control group. However, superoxide radicals in the "microwave + 0.25 % catechin" and "microwave + 0.5 % catechin" groups were 11% and 12% lower, respectively, compared with the catechin-free group.
Microwave exposure significantly increased levels of thiobarbituric acid-reactive substances, carbonyl group values, and lipofuscin contents, but catechins partially overcame the effects of the microwave irradiation.
In conclusion, oxidative damage was induced by microwave exposure. However, green tea catechin supplementation significantly reduced oxidative damage by weakening the free radical generating system, and strengthening of the antioxidative system.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

not stated/no funding

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