Thyroid hormones are involved in 5′-nucleotidase modulation in soluble fraction of cardiac tissue

AimsTo investigate the role of TH (thyroid hormones) in 5′-nucleotidase activity and expression in cardiac soluble fraction (SF).Main methodsMale Wistar rats received daily injections of T4 (10, 25 or 50 μg T4/100 g body weight) for 14 days to develop a hyperthyroidism condition. Thyroidectomy was performed in other animals to mimic hypothyroidism, and 14 days after surgery they were submitted to TH replacement therapy.Key findingsT4 reduced the 5′-nucleotidase activity (T4-25, P < 0.05 and T4-50, P < 0.01) in the SF. Conversely, hypothyroidism significantly increased the 5′-nucleotidase activity in this fraction (P < 0.001) and TH replacement therapy reversed the latter result (P < 0.001 compared to hypothyroid group). The analysis of protein expression in the SF showed that 5′-nucleotidase was more expressed in hypothyroid than in the control group and that the phosphorylated state of PKC observed in this condition may contribute to a possible mechanism of 5′-nucleotidase modulation by thyroid status.SignificanceTaken together, these data reveal that TH can influence adenosine production by modulating 5′-nucleotidase activity and expression, which may contribute to the cardioprotective effect and the maintenance of cardiac function under TH privation.