Angiotensin receptor type 1 mRNA in human right ventricular endomyocardial biopsies: downregulation in heart failure

Atrial angiotensin II receptors type 1 (AT1) are downregulated in end-stage human heart failure at mRNA and protein level. The present study investigated whether AT1 ventricular mRNA content was reduced in myocardial biopsies from heart failure patients.

AT1 mRNA was quantitated in right ventricular endomyocardial biopsies from 16 patients with decreased left ventricular function (LVEF 36 +/- 3%) due to dilated cardiomyopathy (DCM) and in biopsies from 12 patients with suspected myocardial disease but normal cardiac function (LVEF 62 +/- 2%). Two biopsies per patient were pooled, RNA was extracted and reverse-transcribed after addition of an AT1 cRNA standard. AT1 standard and wild-type RNA were amplified with the same primers in the same PCR tube. The PCR products were hybridized to a microtiter plate and detected and quantitated by an ELISA system. Glyceraldehyde phosphate dehydrogenase (GAPDH) mRNA was determined in the same samples as AT1 mRNA.

In the biopsies from 16 patients with heart failure, a 68% decrease in AT1 mRNA content was found in comparison with 12 controls (heart failure 94 +/- 15 AT1 mRNA copies/ng RNA; controls 297 +/- 45; P < 0.001). Relating AT1 mRNA content to GAPDH mRNA confirmed the specific decrease in AT1 mRNA (AT1/GAPDH: heart failure 1.3 +/- 0.15; controls 3.4 +/- 0.5; p < 0.002). The best correlation between AT1 mRNA content and clinical parameters was found for right ventricular ejection fraction (r = 0.59, P < 0.01).

The quantitative RT-PCR procedure indicated a loss of ventricular AT1 mRNA in human heart failure which corresponds to the loss of AT1 protein described previously. It may underlie the decrease in AT1 protein expression in human heart failure.