Expression of mRNA encoding G protein-coupled receptors involved in congestive heart failure

Congestive heart failure (CHF) induces changes in the neurohumoral system and gene expression in viable myocardium. Several of these genes encode G protein-coupled receptors (GPCRs) involved in mechanisms which compensate for impaired myocardial function. We used real-time quantitative RT-PCR (Q-RT-PCR) to investigate the expression of mRNA encoding 15 different GPCRs possibly involved in CHF, and the effect of normalisation to GAPDH mRNA (GAPDH) or 18S rRNA (18S). CHF was induced in rats by coronary artery ligation, with sham-operated controls (Sham). After 6 weeks, mRNA expression in viable left ventricular myocardium was determined using both 18S and GAPDH as the normalisation standard. An apparent 30% reduction in GAPDH mRNA levels vs. 18S in CHF compared to Sham, although not significant in itself, influenced the interpretation of regulation of other genes.Thus, levels of mRNA encoding receptors for angiotensin II (AT₁), endothelin (ET_A, ET_B) and the muscarinic acetylcholine (mACh) receptor M₁ increased significantly in CHF only when normalised to GAPDH. Levels of mRNA encoding the mACh receptors M₃ and M₄ and the serotonin receptors 5-HT_2A and 5-HT₄ increased, whereas α_1D-adrenoceptor mRNA decreased in CHF irrespective of the normalisation standard. No significant change was detected for M2 and M5 mACh receptors or α_1A-, α_1B-, β₁- or β₂-adrenoceptors. Q-RT-PCR is a sensitive and powerful method to monitor changes in GPCR mRNA expression in CHF. However, the normalisation standard used is important for the interpretation of mRNA regulation. This article is accompanied by the Invited Editorial "Pitfalls in the normalization of real-time polymerase chain reaction data" by M. C. Hendriks-Balk et al. which can be found under