Effect of tachycardia on mRNA andf protein expression of the principal components of the lipolytic system in the rat's heart ventricles.

There is a convincing piece of evidence showing that most of free fatty acids (FFA) entering cardiomyocytes are first esterified into triacylglycerols (TG) before being oxidized or used for synthesis of complex lipids. The enzyme adipose triglyceride lipase (ATGL) initiates lipolysis of TG by hydrolyzing the first ester bond of the compound. As a result, free fatty acid and diacylglycerol (DG) are released in that process. Finally, DG may be further hydrolyzed by the enzyme hormone sensitive lipase (HSL). The aim of the present study was to examine effect of tachycardia on mRNA and protein expression of ATGL, CGI-58 (an activator of ATGL), G0S2 (an inhibitor of ATGL) and HSL in the left and right ventricle of the rat. The experiments were carried out on male Wistar rats, 240 - 260 grams of body weight. After anesthesia, two electrodes were inserted in the right jugular vein and connected to SC-04 stimulator. The rats were randomly allocated into one of the three groups, namely: control, 30 min and 60 min of the heart stimulation at the rate of 600 times/min. The expressions of ATGL, CGI-58, G0S2 and HSL were evaluated at both gene and protein levels using real-time PCR and Western Blot analysis, respectively. Both 30 and 60 min stimulation reduced ATGL, HSL, CGI-58 and G0S2 mRNA content in the left ventricle. The stimulation had only insignificant impact on ATGL, HSL and CGI-58 transcript levels in the right ventricle. Interestingly, Western Blot analysis showed that the stimulation, regardless of the time, reduced the ATGL and G0S2 protein expression, but did not change the CGI-58 and HSL expression in the left ventricle. Furthermore, in the right ventricle, the protein expressions of ATGL, HSL and G0S2 decreased after stimulation. In conclusion, the obtained results clearly show that tachycardia affects both mRNA and protein expression of particular compounds of the TG lipolytic system in the heart ventricles. Additionally, there are marked differences in the expressions of the examined compounds between the ventricles.