Interaction Of Sympathetic Nervous System And Renin Angiotensin System In Systemic Circulation Of Cardiac Hypertrophic Rat Model With Gα Protein Expression Interface
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Date
2010-09
Authors
Mohamad Hussain, Nurjannah
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
The present study investigates the interrelation between sympathetic nervous system (SNS) and renin angiotensin system (RAS) in cardiac hypertrophy. Haemodynamic studies were performed to evaluate the vasoconstriction responses of adrenoceptors (i.e. α1- and β1- adrenoceptors) and angiotensin II type 1 receptors (AT1) to understand the functional role of SNS and RAS respectively using the cardiac hypertrophic rat model. Furthermore, the mRNA expression studies of Gα proteins via real time-PCR (RT-PCR) were also conducted to assess 2 isotypes from 3 different groups of Gα proteins which are Gαs, Gαi and Gαq/11 proteins in the rat’s heart. WKY rats were used and cardiac hypertrophy was induced subcutaneously with 2 doses of isoproterenol (5 mg/kg) and 40 mg/kg of caffeine twice daily by gavage as 1% solution for 7 days. In addition, blockers namely atenolol, doxazosin and losartan were administered to investigate the antagonistic features of the respective drugs in blocking the intended receptors, in order to contemplate the receptors reaction and interpret the expression of Gα protein. Significant increments in the mean heart to body index and MAP baseline values were observed in cardiac hypertrophic rats compared to the WKY rats which depicted sympathetic activation. Moreover, histological evaluation of the heart sections confirmed cardiac hypertrophy in the rat model. Reduced functionality of α1- adrenoceptors in cardiac hypertrophic rats was suggested to counteract persistent SNS stimulation caused by the increased functionality of β1-adrenoceptors which was made apparent by the Gαs45 mRNA expression amplification in the hypertrophic heart.
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Keywords
Nervous System And Renin Angiotensin System , Gα Protein Expression Interface