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.