The full cardiac G protein-coupled receptor repertoire reveals chamber-specific expression patterns

Cardiac function is regulated by many hormones and neurotransmitters which exert their physiological effects through the activation of G protein-coupled receptors (GPCRs). Here, we quantified the expression of 395 endoGPCRs (all GPCRs excluding taste and odorant receptors) in male mouse right and left atria and ventricles by using high-throughput real-time RT-PCR and focused on the 135 most highly expressed transcripts. No cardiac functional data is available for almost half of these receptors. Cluster analysis allowed us to link GPCR expression patterns to cardiac function. Indeed, ventricles and atria are both contractile; however, the latter, and especially the right atrium, are central to the generation and regulation of cardiac rhythm. Accordingly, the right atrium exhibited the most specific signature whereas the vast majority of GPCRs found in ventricles were evenly expressed in both the right and left chambers. RT-PCR data were confirmed at the protein level for six selected transcripts (ETA, EP1, PAR1, Sfrp1, CCR2 and AT1a) and at the functional level in isolated mouse ventricular cardiomyocytes for the glutamate metabotropic receptor 1b. Twenty hearts were dissected from 8-week-old C57BL/6 male mice. Total RNAs were prepared from pooled cardiac chambers: right atria (RA) including the SAN, left atria (LA), right (RV) and left ventricles (LV) with 3 replicates for each.