Short-Term Thyroid Hormone Excess Affects the Heart but
               Does not Affect Adrenal Activity in Rats

Szkudlarek, Ariani Cavazzani; Aldenucci, Bruno; Miyagui, Nelson Itiro; Silva, Ilana Kassouf; Moraes, Rosana Nogueira; Ramos, Helton Estrela; Fogaça, Rosalva Tadeu Hochmuller

doi:10.5935/abc.20140014

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Original Articles • Arq. Bras. Cardiol. 102 (3) • Apr 2014 • https://doi.org/10.5935/abc.20140014 copy

Short-Term Thyroid Hormone Excess Affects the Heart but Does not Affect Adrenal Activity in Rats

Authorship SCIMAGO INSTITUTIONS RANKINGS

Background:

Hyperthyroidism (Hy) exerts a broad range of influences on a variety of physiological parameters. Its disruptive effect on cardiovascular system is one of its most remarkable impacts. Moreover, Hy has been clinically associated with stress - induced hyperactivation of the hypothalamic-pituitary-adrenal axis.

Objective:

Evaluate the impact of short-term Hy on cardiac performance and adrenal activity of rats.

Methods:

Induction of Hy in Wistar rats through injections of T3 (150 µg/kg) for 10 days (hyperthyroid group - HG) or vehicle (control group). The cardiovascular performance was evaluated by: echocardiography (ECHO); heart weight/body weight (mg/gr) ratio; contractility of isolated papillary muscles (IPM) and direct measurement of blood pressures. Adrenal activity was evaluated by adrenal weight/body weight (mg/gr) ratio and 24-hour fecal corticosterone (FC) levels on the, 5^th and 10^th days of T3 treatment.

Results:

In HG, the ECHO showed reduction of the End Systolic and End Diastolic Volumes, Ejection, Total Diastolic and Isovolumic Relaxation Times, Diastolic and Systolic Areas and E/A ratio. Heart Rate, Ejection Fraction and Cardiac Output increased. The heart weight/body weight ratio was higher. Similarly, in IPM, the maximum rate of force decay during relaxation was higher in all extracellular calcium concentrations. Systolic blood pressure (SBP) levels were higher. (p ≤ 0.05). On the other hand, there was no difference in the adrenal weight/body weight ratio or in the 24-hour FC levels.

Conclusions:

Hy induces positive inotropic, chronotropic and lusitropic effects on the heart by direct effects of T3 and increases SBP. Those alterations are not correlated with changes in the adrenal activity.

Thyroid Hormones; Hyperthyroidism / complications; Adrenal Glands; Rats; Cardiovascular Diseases

	ESV	EDV	IRT	ICT	TDT	HR	ET	EF
CG	0.19 ± 0.01	0.52 ± 0.02	27 ± 0.006	16 ± 0.002	131 ± 0.01	270 ± 14	84 ± 0.001	63 ± 0.5
HG	0.12^* * p < 0.05 compared to control animals. Time - in msec. Volume - in mL. ESV: end systolic volume; EDV: end diastolic volume; IRT: isovolumic relaxation time; ICT: isovolumic contraction time; TDT: total diastolic time; HR: heart rate; EF: ejection fraction. ET: Ejection time. ± 0.01	0.43^* * p < 0.05 compared to control animals. Time - in msec. Volume - in mL. ESV: end systolic volume; EDV: end diastolic volume; IRT: isovolumic relaxation time; ICT: isovolumic contraction time; TDT: total diastolic time; HR: heart rate; EF: ejection fraction. ET: Ejection time. ± 0.02	18^* * p < 0.05 compared to control animals. Time - in msec. Volume - in mL. ESV: end systolic volume; EDV: end diastolic volume; IRT: isovolumic relaxation time; ICT: isovolumic contraction time; TDT: total diastolic time; HR: heart rate; EF: ejection fraction. ET: Ejection time. ± 0.002	15 ± 0.001	100^* * p < 0.05 compared to control animals. Time - in msec. Volume - in mL. ESV: end systolic volume; EDV: end diastolic volume; IRT: isovolumic relaxation time; ICT: isovolumic contraction time; TDT: total diastolic time; HR: heart rate; EF: ejection fraction. ET: Ejection time. ± 0.004	380^* * p < 0.05 compared to control animals. Time - in msec. Volume - in mL. ESV: end systolic volume; EDV: end diastolic volume; IRT: isovolumic relaxation time; ICT: isovolumic contraction time; TDT: total diastolic time; HR: heart rate; EF: ejection fraction. ET: Ejection time. ± 9.2	59^* * p < 0.05 compared to control animals. Time - in msec. Volume - in mL. ESV: end systolic volume; EDV: end diastolic volume; IRT: isovolumic relaxation time; ICT: isovolumic contraction time; TDT: total diastolic time; HR: heart rate; EF: ejection fraction. ET: Ejection time. ± 0.001	72^* * p < 0.05 compared to control animals. Time - in msec. Volume - in mL. ESV: end systolic volume; EDV: end diastolic volume; IRT: isovolumic relaxation time; ICT: isovolumic contraction time; TDT: total diastolic time; HR: heart rate; EF: ejection fraction. ET: Ejection time. ± 1.2

	SO	CO	AV	DTEW	Diast. area	Syst. area	Tei index	E/A
CG	0.33 ± 0.01	89 ± 7.98	127 ± 0.002	45 ± 0.002	0.99 ± 0.014	0.54 ± 0.01	0.5 ± 0.03	1.9 ± 0.24
HG	0.31 ± 0.02	118^* * p < 0.05 compared to control animals. Time - in msec. Volume - in mL. Area – in cm2. SO: systolic output; CO: cardiac output; Diast. area: Diastolic area; Syst. area: Systolic area; AV: A variable; DTEW: deceleration time of E wave; E/A: ratio of the maximal early to atrial mitral flow velocities. ± 6.82	92^* * p < 0.05 compared to control animals. Time - in msec. Volume - in mL. Area – in cm2. SO: systolic output; CO: cardiac output; Diast. area: Diastolic area; Syst. area: Systolic area; AV: A variable; DTEW: deceleration time of E wave; E/A: ratio of the maximal early to atrial mitral flow velocities. ± 0.002	43 ± 0.002	0.9^* * p < 0.05 compared to control animals. Time - in msec. Volume - in mL. Area – in cm2. SO: systolic output; CO: cardiac output; Diast. area: Diastolic area; Syst. area: Systolic area; AV: A variable; DTEW: deceleration time of E wave; E/A: ratio of the maximal early to atrial mitral flow velocities. ± 0.02	0.42^* * p < 0.05 compared to control animals. Time - in msec. Volume - in mL. Area – in cm2. SO: systolic output; CO: cardiac output; Diast. area: Diastolic area; Syst. area: Systolic area; AV: A variable; DTEW: deceleration time of E wave; E/A: ratio of the maximal early to atrial mitral flow velocities. ± 0.01	0.54 ± 0.02	1.57^* * p < 0.05 compared to control animals. Time - in msec. Volume - in mL. Area – in cm2. SO: systolic output; CO: cardiac output; Diast. area: Diastolic area; Syst. area: Systolic area; AV: A variable; DTEW: deceleration time of E wave; E/A: ratio of the maximal early to atrial mitral flow velocities. ± 0.35

CG 1	HG 1	CG 5	HG 5^* * p < 0.05 compared to control animals. Concentration, in ng/g of feces. 1: 1st day of injection; 5: 5th day of injection; 10: 10th day of injection.	CG 10	HG 10
273,19 ± 62,73	317,32 ± 48,96	272,94 ± 30,83	613,54 ± 104,74	305,82 ± 65,79	361,27 ± 65,99

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[1] Mailing Address: Ariani Cavazzani Szkudlarek. Alameda Prudente de Moraes, 732, apto. 54, Centro. Postal Code 80430-220, Curitiba, PR - Brazil. E-mail: arianiinaira@yahoo.com.br