Gr. Sadani et Gd. Nadkarni, CHANGES IN LIPID PEROXIDE LEVELS AND THE ACTIVITY OF REACTIVE OXYGEN SCAVENGING SYSTEMS IN THYROID-TISSUE AFTER EXPOSURE TO RADIOACTIVE IODINE IN RATS, Thyroid, 7(6), 1997, pp. 937-941
Exposure to ionizing radiation causes radiolysis of water in tissues l
eading to generation of reactive oxygen species (ROS), which are known
to affect the antioxidant defense systems and induce lipid peroxidati
on (LP). Use of radioactive iodine (I-131) for diagnosis and therapy o
f thyroid disorders may also generate ROS in the thyroid. Early (24 an
d 48 hours) and late (18 days) effects of subablation doses of I-131 (
370/555/1110 kBq) on the antioxidant defense and LP in the thyroid tis
sues have been studied. LP was elevated in all I-131 treated groups by
10% to 41%. Although there was no change in catalase (CAT), the super
oxide dismutase (SOD) and glutathione peroxidase (GPx) activities show
ed evidence of change from 48 hours onwards-SOD decreased by 32% to 56
% and GPx increased by 15% to 43%. Nonprotein thiols (reduced glutathi
one, GSH) showed an elevation of 16% at 24 hours, but later declined b
y 15% by day 18 after 370 KBq of I-131. Thus, the increase in LP obser
ved may be due to beta irradiation induced ROS by I-131. The parallel
decrease in SOD could be due to inactivation by ROS. The increase in G
Px may be a consequence of induction due to elevated LP and/or ROS, wh
ich may be inadequate to lower the LP. In spite of elevated LP, the th
yroid function appears to be normal.