Upregulation of mRNA myocardium calcium handling in rats submitted to exercise and food restriction.

BACKGROUND Chronic exercise and food restriction (FR) have directionally opposite changes in transcription of molecular structures of calcium handling and thyroid hormone (TH) status. OBJECTIVE Evaluate the association of chronic exercise and FR on serum thyroid hormones and gene transcription of molecular structures of intracellular calcium transients and thyroid receptors in myocardium of rats. METHODS Male Wistar Kyoto rats, divided into two groups: control (C, n = 7), FR (R50, n = 7), chronic exercise (EX, n = 7) and chronic exercise + FR (EX50, n = 7). FR was of 50% and exercise was swimming (1 hour/day, 5 days/week, during 12 weeks). Serum concentrations of T3, T4 and TSH were determined. The mRNA gene expression of the sarcoplasmatic reticulum calcium pump (SERCA2a), phospholamban (PLB), Na+/Ca+2 exchanger (NCX), calcium channel L-type (L-channel), ryanodine (RYR), calsequestrin (CQS) and HT receptor (TRα1 and TRβ1) of the myocardium was performed by PCR real-time. RESULTS FR reduced serum levels of T4 and TSH and TRα1 mRNA and increased the expression of PLB, NCX and L-channel. Exercise increased the TRβ1 receptor, L-channel and NCX. The association of exercise and FR reduced plasma T4 and TSH, TRβ1 mRNA increase, SERCA2a, NCX and PLB, and there was a significant correlation of TRβ1 with CQS and NXC. CONCLUSION Chronic exercise and food restriction increased the mRNA of transient Ca2+ proteins; however, TH-receptor axis cannot participate in the transcription of mRNA of myocardial calcium transient proteins.