Free Radical Biology & Medicine, Vol. 11, pp. 299-306, 1991 Printed in the USA. All rights reserved.
0891-5849/91 $3.00 + .00 Copyright ~ 1991 Pergamon Press plc
Original Contribution INCREASED SOD ACTIVITIES AND DECREASED LIPID PEROXIDE LEVELS INDUCED BY LOW DOSE X IRRADIATION IN RAT ORGANS
KIYONORI YAMAOKA, REI EDAMATSU, and AKITANEMORI* Department of Neurochemistry, Institute for Neurobiology, Okayama University Medical School, 2-5-1 Shikata-cho, Okayama 700, Japan (Received 7 September 1990; Revised and Accepted 1 April 1991)
Abstract--After a single exposure to doses ranging from 0.05 to 0.50 Gy, the SOD activities in immune organs of the irradiated rats, at 4 h after whole-body X irradiation, showed significant increases by 50 to 90% (hereinafter p < 0.05) in comparison with the control groups. The dose in the brain and liver showed tendencies to increase by 30 to 50% for doses ranging from 0.50 to 2.50 Gy. The levels of TBARS (lipid peroxides) in immune organs decreased significantly by 20 to 50% in contrast with the control groups for doses ranging from 0.10 to 1.00 Gy. Decreases by 20 to 30% were observed in brains and livers for doses near 0.50 Gy. When the dose was 0.25 Gy, the SOD activities in the spleen showed a persistent radiation-induced increase for at least 12 weeks, livers for 8 weeks, brains and thymuses for 4 weeks, and bone marrows for about 1 week. The TBARS levels in the brain and thymus showed persistent decreases due to irradiation for at least 12 weeks, and those in bone marrows for 8 h. Keywords--Low dose irradiation, Induction of SOD, Decrease in lipid peroxides, Free radicals
INTRODUCTION
whether SOD is inductively synthesized, and whether peroxidization of lipids is reduced.
SOD activities in living bodies drop, depending on the concentration of active oxygen generated by high dose irradiation.1 However in the case of low dose irradiation, SOD activities might increase. This is suggested by the finding that SOD was inductively synthesized in rats under a certain high level of oxygen partial pressure. 2 Another line of evidence is that metallothionein, which has an effect similar to that of SOD, was inductively synthesized due to stress tending to increase lipid peroxides in living bodies, including X irradiation. 3 Furthermore, there are also many relevant reports that SOD inhibits peroxidization of lipid induced by 0 2 producing systems. Moreover, there are reports, although just a few, that indicate such a protective phenomenon may take place not only in vitro but in vivo. 4,5 After a preliminary examination, 6'7 we exposed rats to whole-body low dose X irradiation, and examined the changes in the SOD activities and T B A R S levels in brains, lungs, livers, thymuses, spleens, and bone marrows, in relation to dose dependency and temporal changes after irradiation. In particular, we examined
MATERIALS AND METHODS
A n i m a l models
Seven-weeks-old male rats (F344/N Sic (Fischer)) were used under identical breeding conditions. Rats were irradiated and dissected as follows: for dose dependency studies, rats were fixed with liquid nitrogen at 4 h after irradiation, because at that time in vivo reactions are reportedly highly sensitive to radiation. 8 As for the temporal changes after irradiation, rats were uniformly irradiated at 0.25 G y (see RESULTS), and rats were fixed with liquid nitrogen at 1, 2, 3, 4, and 8 h, 1, 2, and 3 days, 1, 2, 3, 4, 8, and 12 weeks after irradiation. Rats were placed on ice and specimens were taken from brain, lungs, liver, thymus, spleen, and bone marrow. The control groups were treated in the same manner except for irradiation in the irradiation groups. One day later and 4 weeks later, the control groups were dissected in the same manner as the irradiation groups. The whole body of each rat was evenly irradiated by X-ray (maximum rated output voltage; 180KeV) from an X-ray generator (Toshiba KXC-18). The doses
*Author to whom correspondence should be addressed. 299
300
K. YAMAOKAet al.
] Control • (n=12) ~
Irradiation (n=8-12) Brain
10,0
Control 0.0
1
8"0 t
Lung
I
1
I
I
1
I
I
#r o,
6"0 4.0 I 2.0 0.0
I!
I
I
I
I
1
I
J
30.0 ._= t9 O Q.
10.0 0.0
t~
t
20.0",
.
I
I
I
I0.0
a O O'J 5.0
0.0 Spleen (p
0891-5849/91 $3.00 + .00 Copyright ~ 1991 Pergamon Press plc
Original Contribution INCREASED SOD ACTIVITIES AND DECREASED LIPID PEROXIDE LEVELS INDUCED BY LOW DOSE X IRRADIATION IN RAT ORGANS
KIYONORI YAMAOKA, REI EDAMATSU, and AKITANEMORI* Department of Neurochemistry, Institute for Neurobiology, Okayama University Medical School, 2-5-1 Shikata-cho, Okayama 700, Japan (Received 7 September 1990; Revised and Accepted 1 April 1991)
Abstract--After a single exposure to doses ranging from 0.05 to 0.50 Gy, the SOD activities in immune organs of the irradiated rats, at 4 h after whole-body X irradiation, showed significant increases by 50 to 90% (hereinafter p < 0.05) in comparison with the control groups. The dose in the brain and liver showed tendencies to increase by 30 to 50% for doses ranging from 0.50 to 2.50 Gy. The levels of TBARS (lipid peroxides) in immune organs decreased significantly by 20 to 50% in contrast with the control groups for doses ranging from 0.10 to 1.00 Gy. Decreases by 20 to 30% were observed in brains and livers for doses near 0.50 Gy. When the dose was 0.25 Gy, the SOD activities in the spleen showed a persistent radiation-induced increase for at least 12 weeks, livers for 8 weeks, brains and thymuses for 4 weeks, and bone marrows for about 1 week. The TBARS levels in the brain and thymus showed persistent decreases due to irradiation for at least 12 weeks, and those in bone marrows for 8 h. Keywords--Low dose irradiation, Induction of SOD, Decrease in lipid peroxides, Free radicals
INTRODUCTION
whether SOD is inductively synthesized, and whether peroxidization of lipids is reduced.
SOD activities in living bodies drop, depending on the concentration of active oxygen generated by high dose irradiation.1 However in the case of low dose irradiation, SOD activities might increase. This is suggested by the finding that SOD was inductively synthesized in rats under a certain high level of oxygen partial pressure. 2 Another line of evidence is that metallothionein, which has an effect similar to that of SOD, was inductively synthesized due to stress tending to increase lipid peroxides in living bodies, including X irradiation. 3 Furthermore, there are also many relevant reports that SOD inhibits peroxidization of lipid induced by 0 2 producing systems. Moreover, there are reports, although just a few, that indicate such a protective phenomenon may take place not only in vitro but in vivo. 4,5 After a preliminary examination, 6'7 we exposed rats to whole-body low dose X irradiation, and examined the changes in the SOD activities and T B A R S levels in brains, lungs, livers, thymuses, spleens, and bone marrows, in relation to dose dependency and temporal changes after irradiation. In particular, we examined
MATERIALS AND METHODS
A n i m a l models
Seven-weeks-old male rats (F344/N Sic (Fischer)) were used under identical breeding conditions. Rats were irradiated and dissected as follows: for dose dependency studies, rats were fixed with liquid nitrogen at 4 h after irradiation, because at that time in vivo reactions are reportedly highly sensitive to radiation. 8 As for the temporal changes after irradiation, rats were uniformly irradiated at 0.25 G y (see RESULTS), and rats were fixed with liquid nitrogen at 1, 2, 3, 4, and 8 h, 1, 2, and 3 days, 1, 2, 3, 4, 8, and 12 weeks after irradiation. Rats were placed on ice and specimens were taken from brain, lungs, liver, thymus, spleen, and bone marrow. The control groups were treated in the same manner except for irradiation in the irradiation groups. One day later and 4 weeks later, the control groups were dissected in the same manner as the irradiation groups. The whole body of each rat was evenly irradiated by X-ray (maximum rated output voltage; 180KeV) from an X-ray generator (Toshiba KXC-18). The doses
*Author to whom correspondence should be addressed. 299
300
K. YAMAOKAet al.
] Control • (n=12) ~
Irradiation (n=8-12) Brain
10,0
Control 0.0
1
8"0 t
Lung
I
1
I
I
1
I
I
#r o,
6"0 4.0 I 2.0 0.0
I!
I
I
I
I
1
I
J
30.0 ._= t9 O Q.
10.0 0.0
t~
t
20.0",
.
I
I
I
I0.0
a O O'J 5.0
0.0 Spleen (p
