Alterations of relaxin and its receptor system components in experimental diabetic cardiomyopathy rats.

High glucose induces apoptosis of cardiomyocytes and fibrosis of cardiac fibroblasts, contributing to diabetic cardiomyopathy. In this work, we explore the production of relaxin alterations and the significance of their receptor system components in the hearts of experimental diabetic cardiomyopathy rats. We measured rat relaxin-1 (equivalent to human relaxin-2), relaxin-3, RXFP1 and RXFP3 mRNA expression in the hearts of experimental diabetic cardiomyopathy rats. Neonatal rat ventricular myocytes (NRVMs) and cardiac fibroblasts were treated with 5.5 mmol/l normal glucose (NG) and 33 mmol/l high glucose (HG) for 0, 6, 12, 24, 48 and 72 h. Rat relaxin-1, relaxin-3, RXFP1 and RXFP3 mRNA expression were determined by real-time PCR. In the present study, we offer the first evidence that Relaxin-1 mRNA significantly increased and Relaxin-3 mRNA expression decreased at 4 and 8 weeks after STZ in the hearts of diabetic rats. In addition, significant down regulation of the mRNA expression of RXFP1 and RXFP3 was observed at 4 w after STZ; however, the mRNA expression levels of RXFP1 and RXFP3 were increased at 8 weeks after STZ. Apoptotic NRVMs induced by high glucose generate a decreased level of relaxin-1 and RXFP1. In HG-administered cardiac fibroblasts, Relaxin-1 mRNA was significantly increased and relaxin-3 mRNA was significantly decreased. Additionally, the mRNA expression of RXFP1 was decreased, and the mRNA expression of RXFP3 was increased. This results showed that an important role of relaxin-2, relaxin-3 and their receptors system in the regulation of diabetic cardiomyopathy.