Abstract
Accumulating evidence has shown that hypothyroidism affects the cardiovascular system, significantly increasing the incidence of cardiovascular diseases. In the present study we investigated the effect of radioactive iodine (I-131)-induced hypothyroidism on several parameters of vascular function, such as nitric oxide (NO), total nitric oxide synthase (NOS) activity and expression of NOS isoforms, as well as on interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α) as indicators of inflammation, in rats. A dose of 150 µCi of 131-I was determined as optimal for establishing the model of hypothyroidism in rats. After administration of 131-I, at the end of month 1, 2, and 4 (n = 3 for each time point), NO, IL-6, and TNF-α in the serum and total NOS activity in the aorta were determined in 150 µCi group, compared to controls. The mRNA and protein expression of endothelial, neuronal, and inducible NOS (eNOS, nNOS, and iNOS) in the rat aorta was also estimated, using quantitative reverse transcription polymerase chain reaction and Western blot, respectively. The levels of IL-6 and TNF-α increased in 150 µCi group; the results were significant at the end of month 2 and 4 for IL-6, and at all time points for TNF-α. The levels of NO decreased significantly at the end of month 2 and 4 in 150 µCi group. The total NOS activity increased significantly in 150 µCi group, at all three time points. Significant changes in the mRNA and protein expression of all three NOS isoforms were observed in 150 µCi group compared to controls. NO, IL-6, TNF-α levels and NOS activity and expression are altered in hypothyroid state, and the underlying mechanism should be further investigated.
Highlights
In many countries, radioactiveiodine (131I or I-131) has been utilized for more than 60 years; for example in China, I-131 treatment has been in use since 1958 [1]
We investigated the effect of 131I-induced hypothyroidism on nitric oxide (NO), total nitric oxide synthase (NOS) activity and expression of NOS isoforms as parameters of vascular function, and on interleukin 6 (IL-6) and TNF-α as indicators of inflammation, in rats
The thyroid radioactivity gradually increased from the low-dose to high-dose group after the 131I administration at the end of month 1, and was markedly decreased in each dose group at the end of month 2 and 4; most of the radioactivity values being similar to the natural background value (Table 3)
Summary
Radioactiveiodine (131I or I-131) has been utilized for more than 60 years; for example in China, I-131 treatment has been in use since 1958 [1]. I-131 is the first choice for the treatment of hyperthyroidism in adults in European countries and the USA. The cumulative incidence of hypothyroidism, in I-131 treated patients with hyperthyroidism caused by Graves’ disease, has been gradually increasing each year, reaching around 80% in adults and Submitted: 12 August 2017/Accepted: 26 October 2017. Accumulating evidence has shown that hypothyroidism seriously affects the cardiovascular system, significantly increasing the incidence of cardiovascular diseases [6, 7]. Both subclinical hypothyroidism and hypothyroidism decrease the cardiac output, increase the peripheral resistance, and impair the endothelial function [6,8]. The vascular endothelium, as the interface between the blood and vessel walls, plays a major role in regulating vascular structure and function [10]
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