INCREASED ANGIOTENSIN-I CONVERTING-ENZYME GENE-EXPRESSION IN THE FAILING HUMAN HEART - QUANTIFICATION BY COMPETITIVE RNA-POLYMERASE CHAIN-REACTION

Local activation of the components of the renin angiotensin system in the heart is regarded as an important modulator of cardiac phenotype a nd function; however, little is known about their presence, regulation , and potential activation in the human heart. To investigate the gene expression of major angiotensin-II-forming enzymes in left ventricles of normal (n = 9) and failing human hearts (n = 20), we established a competitive RNA-polymerase chain reaction (PCR) for mRNA quantificati on of angiotensin-I converting enzyme (ACE) and human heart chymase. F or each gene, competitor RNA targets with small internal deletions wer e used as internal standards to quantify the original number of transc ripts and to control reverse transcription and PCR. In PCR, each targe t and the corresponding competitor were amplified by competing for the same primer oligonucleotides. The variability of ACE RNA-PCR was 11% indicating a high reproducibility of this method. In addition, ACE mRN A levels obtained by competitive RNA-PCR correlated favorably with tra ditional slot blot hybridization (r = 0.69, n = 10; P < 0.05). Compare d with nonfailing hearts, the number of ACE transcripts referred to 10 0 ng of total RNA was increased threefold in patients with chronic hea rt failure (4.2+/-2.5 vs. 12.8+/-6 x 10(5); P < 0.0005), In contrast, no significant difference was found in chymase gene expression between normal and failing hearts, Thus, the expression of the cardiac ACE bu t not of human heart chymase is upregulated in failing human heart ind icating an activation of the cardiac renin-angiotensin system in patie nts with advanced heart failure.