Evaluation of acute physiological and molecular alterations in surgically developed hypothyroid Wistar rats

Patel, Meenakshi; Mishra, Vinay; Pawar, Vaibhavi; Ranvir, Ramchandran; Sundar, Rajesh; Dabhi, Rajas

doi:10.4103/0976-500x.110891

Cited by 13 publications

(10 citation statements)

References 19 publications

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“…This finding confirms previous results, which also observed a lower tolerance to exercise in rats with experimental hypothyroidism (26). The importance of thyroid hormone in physical performance may be associated with the regulation of genetic expression of α and β myosin heavy chain in the myocardium by THs (27). Previous studies in rodents found that TH increases the expression of α myosin heavy chain (αMHC) and, decreases the expression of β myosin heavy chain (βMHC) (28).…”

Section: Relative Weight Of the Soleus Musclesupporting

confidence: 90%

The thyroid hormone receptor β-selective agonist GC-1 does not affect tolerance to exercise in hypothyroid rats

Gonçalves

Tolentino

Souza

et al. 2015

Arch. Endocrinol. Metab.

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Objective: Investigate the effect of GC-1 on tolerance to exercise in rats with experimental hypothyroidism. Materials and methods: Hypothyroidism was induced with methimazole sodium and perchlorate treatment. Six groups with eight animals were studied: control group (C), hypothyroid group without treatment (HYPO); hypothyroidism treated with physiological doses of tetraiodothyronine (T 4 ) or 10 times higher (10×T 4 ); hypothyroidism treated with equal molar doses of GC-1 (GC-1) or 10 times higher (10×GC-1). After eight weeks, each animal underwent an exercise tolerance test by measuring the time (seconds), in which the rats were swimming with a load attached to their tails without being submerging for more than 10 sec. After the test, the animals were killed, and blood samples were collected for biochemical analysis, and the heart and soleus muscle were removed for weighing and morphometric analysis of the cardiomyocyte. Results: Hypothyroidism significantly reduced tolerance to exercise and, treatment with GC-1 1× or T 4 in physiological doses recover tolerance test to normal parameters. However, high doses of T 4 also decreased tolerance to physical exercise. Conversely, ten times higher doses of GC-1 did not impair tolerance to exercise. Interestingly, hypothyroidism, treated or not with T4 in a physiological range, GC-1 or even high doses of GC-1 (10X) did not change cardiomyocyte diameters and relative weight of the soleus muscle. In contrast, higher doses of T 4 significantly increased cardiomyocyte diameter and induced atrophy of the soleus muscle. Conclusion: Unlike T 4 , GC-1 in high doses did not modify tolerance to physical exercise in the rats with hypothyroidism. Arch Endocrinol Metab. 2015;59(2):141-7

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Section: Relative Weight Of the Soleus Musclesupporting

confidence: 90%

The thyroid hormone receptor β-selective agonist GC-1 does not affect tolerance to exercise in hypothyroid rats

Gonçalves

Tolentino

Souza

et al. 2015

Arch. Endocrinol. Metab.

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“… 19 α-MHC had a fast ATPase activity and higher velocity of fiber shortening than β-MHC, so α-MHC: β-MHC ratio in the heart can determine cardiac contractility. 20 Hypothyroidism in adult rats leads to the increase expression of β-MHC and decrease velocity of fiber shortening and, then, diminishes cardiac contractility. 20 , 21 Chizzonite R.A. et al reported that an increase in α-MHC observed after birth was concurrent with a remarkable increase in the serum level of thyroid hormones.…”

Section: Discussionmentioning

confidence: 99%

Effect of Fetal Hypothyroidism on Cardiac Myosin Heavy Chain Expression in Male Rats

Yousefzadeh¹,

Jeddi²,

Alipour³

2016

Arquivos Brasileiros De Cardiologia

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Background:Thyroid hormone deficiency during fetal life could affect the cardiac function in later life. The mechanism underlying this action in fetal hypothyroidism (FH) in rats has not been elucidated thus far.Objective:The aim of this study is to evaluation the effect of FH on cardiac function in male rats and to determine the contribution of α-myosin heavy chain (MHC) and β-MHC isoforms.Methods:Six pregnant female rats were randomly divided into two groups: The hypothyroid group received water containing 6-propyl-2-thiouracil during gestation and the controls consumed tap water. The offspring of the rats were tested in adulthood. Hearts from the FH and control rats were isolated and perfused with langendroff setup for measuring hemodynamic parameters; also, the heart mRNA expressions of α- MHC and β-MHC were measured by qPCR.Results:Baseline LVDP (74.0 ± 3.1 vs. 92.5 ± 3.2 mmHg, p < 0.05) and heart rate (217 ± 11 vs. 273 ± 6 beat/min, p < 0.05) were lower in the FH rats than controls. Also, these results showed the same significance in ±dp/dt. In the FH rats, β-MHC expression was higher (201%) and α- MHC expression was lower (47%) than control.Conclusion:Thyroid hormone deficiency during fetal life could attenuate normal cardiac functions in adult rats, an effect at least in part due to the increased expression of β-MHC to α- MHC ratio in the heart.

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“…Knowing that rats do not have heat-activated sweating process, such behaviors have been reportedly addressed for the purpose of maximizing cutaneous evaporative heat loss when exposed to HS [19,31,32]. Correspondingly, links between behavioral thermoregulation to higher T core have also been proven [33], as well as formerly by our research group [34]. It is also worthy to point out that the paws and tails of the thermally stressed rats appeared more reddish, clearly signifying greater blood shifting from deep splanchnic to more peripheral body sites, so as to dissipate the extra heat load [19,32,34].…”

Section: Discussionmentioning

confidence: 99%

The Wolff–Chaikoff effect ameliorates heat stress in rats

Al-Tamimi¹,

Al-Dawood²,

Mahasneh³

2019

Anim Biotelemetry

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Background: The thyroid gland contributes immensely to the basal metabolic rate, and hence, thermogenesis in mammals. Its response to the thermal environment is, however, slow and may require several days to adjust. A rapid thyrosuppressive mechanism ("Wolff-Chaikoff" phenomenon; WC) is inducible by high dietary iodine ingestion. The current study aimed to examine the WC on thermophysiology of rats exposed to acute heat stress (HS). Biotelemetry was used to assess real-time core body temperature (T core), locomotive activity (LA) and heart rate (HR) in rats (N = 12). Animals were randomly assigned to two treatment groups: a control (CN) group had ad libitum access to tap water throughout the trial; a second group (KI) received potassium iodide (0.5%) in drinking water, 3 h before HS. Climatic conditions during the 10-day experimental period were set to 4 days at thermoneutrality (TN; T a = 23.60 ± 0.05 °C), then HS (T a = 33.22 ± 0.25 °C, for 4 h) and finally back to TN until the end of trial. Serum samples were collected right after the HS, to measure free thyroxine (FT4), triiodothyronine (FT3) and total antioxidant capacity (TAO), from 12 other equivalent rats. Results: The KI induced the WC, as evidenced with lower FT3 (1.66 and 1.91 ± 0.08 pg/mL) than the CN treatment, respectively. This momentary goitrogenic response by KI mitigated hyperthermia, compared to CN (T core maxima of 38.90 and 39.54 ± 0.09 °C). Furthermore, KI resulted in higher TAO than KI-free rats (238.30 and 198.80 ± 9.10 µM copper reducing equivalents). While instigating an instant suppression in LA, KI caused a delayed 25% elevation in HR along with a rebound in T core , likely due to the "escape phenomenon. " Conclusions: The employed WC protocol alleviated HS impact on rats. Research on other mammals awaits further investigation.

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Evaluation of acute physiological and molecular alterations in surgically developed hypothyroid Wistar rats

Cited by 13 publications

References 19 publications

The thyroid hormone receptor β-selective agonist GC-1 does not affect tolerance to exercise in hypothyroid rats

The thyroid hormone receptor β-selective agonist GC-1 does not affect tolerance to exercise in hypothyroid rats

Effect of Fetal Hypothyroidism on Cardiac Myosin Heavy Chain Expression in Male Rats

The Wolff–Chaikoff effect ameliorates heat stress in rats

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