Transient receptor potential canonical (TRPC) proteins have been identified as a family of plasma membrane calcium-permeable channels. TRPC proteins can be activated by various stimuli and act as cellular sensors in mammals. Stretch-activated ion channels (SACs) have been proposed to underlie cardiac mechano-electric feedback (MEF), although the molecular entity of SAC remains unknown. There is evidence suggesting that transient receptor potential canonical 1 (TRPC1) is a stretch-activated ion channel. As a non-selective cation channel, TRPC1 may cause stretch-induced depolarization and arrhythmia and thus may contribute to the MEF of the heart. In this study, we examined the expression patterns of TRPC1 in detail at both the mRNA and protein levels in rat hearts. We isolated total RNA from the left and right atria, and the left and right ventricles, and detected TRPC1 mRNA in these tissues using reverse-transcriptase polymerase chain reaction (RT-PCR). To study the protein localization and targeting, we performed immunohistochemistry and immunofluorescence labeling with the antibody against TRPC1. TRPC1 was detected in the cardiomyocytes of the ventricle and atrium at both the mRNA and protein levels. The cell membrane and T-tubule showed strong fluorescence labeling in the ventricular myocytes. Purkinje cells, the endothelial cells and smooth muscle cells of the coronary arterioles also displayed TRPC1 labeling. No TRPC1 was detected in fibroblasts. In conclusion, TRPC1 is widely expressed in the rat heart, including in working cells, Purkinje cells and vascular cells, suggesting that it plays an important role in the heart. The specific distribution pattern offered a useful insight into its function in adult rat ventricular cells. Further investigations are needed to clarify the role of TRPC1 in regulating cardiac activity, including cardiac MEF
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