Increased calcium influx mediates increased cardiac stiffness in hyperthyroid rats

Levick, Scott and Fenning, Andrew and Brown, Lindsay (2005) Increased calcium influx mediates increased cardiac stiffness in hyperthyroid rats. Cell Biochemistry and Biophysics, 43 (1). pp. 53-60. ISSN 1085-9195

Abstract

Cardiac remodeling (hypertrophy and fibrosis) and an increased left ventricular diastolic stiffness characterize models of hypertension such as the SHR and DOCA-salt hypertensive rats. By contrast, hyperthyroidism induces hypertrophy and hypertension, yet collagen expression and deposition is unchanged or decreased, whereas diastolic stiffness is increased. We determined the possible role of increased calcium influx in the development of increased diastolic stiffness in hyperthyroidism by administering verapamil (15 mg/[kg x d] orally) to rats given triiodothyronine (T3) (0.5 mg/[kg x d] subcutaneously for 14 d). Administration of T3 significantly increased body temperature (control: 36.7 +/- 0.2 degrees C; T3: 39.6 +/- 0.2 degrees C), left ventricular wet weight (control: 2.09 +/- 0.02 mg/kg; T3 3.07 +/- 0.07 mg/kg), systolic blood pressure (control: 128 +/- 5 mmHg; T3: 156 +/- 4 mmHg), and left ventricular diastolic stiffness (control: 20.6 +/- 2.0; T3: 28.8 +/- 1.4). Collagen content of the left ventricle was unchanged. Contractile response to noradrenaline in thoracic aortic rings was reduced. Relaxation in response to acetylcholine (ACh) was also reduced in T3-treated rats, whereas sodium nitroprusside response was unchanged. Verapamil treatment of hyperthyroid rats completely prevented the increased diastolic stiffness and systolic blood pressure while attenuating the increased body temperature and left ventricular weight; collagen content remained unchanged. ACh response in thoracic aortic rings was restored by verapamil. Thus, in hyperthyroid rats, an increased calcium influx is a potential mediator of the increased diastolic stiffness independent of changes in collagen.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Permanent restricted access to published version due to publisher copyright policy.
Depositing User: Professor Lindsay Brown
Faculty / Department / School: Historic - Faculty of Sciences - Department of Biological and Physical Sciences
Date Deposited: 30 Oct 2011 05:06
Last Modified: 03 Jul 2013 00:50
Uncontrolled Keywords: calcium; diastolic stiffness; hyperthyroidism; rat; endothelial dysfunction
Fields of Research (FOR2008): 06 Biological Sciences > 0699 Other Biological Sciences > 069999 Biological Sciences not elsewhere classified
06 Biological Sciences > 0606 Physiology > 060699 Physiology not elsewhere classified
11 Medical and Health Sciences > 1102 Cardiovascular Medicine and Haematology > 110201 Cardiology (incl. Cardiovascular Diseases)
Socio-Economic Objective (SEO2008): E Expanding Knowledge > 97 Expanding Knowledge > 970106 Expanding Knowledge in the Biological Sciences
E Expanding Knowledge > 97 Expanding Knowledge > 970111 Expanding Knowledge in the Medical and Health Sciences
URI: http://eprints.usq.edu.au/id/eprint/19885

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