Expression of Angiotensin AT1 and AT2 Receptors in Adult Rat Cardiomyocytes after Myocardial Infarction : A Single-Cell Reverse Transcriptase-Polymerase Chain Reaction Study

摘要

The effector hormone of the renin-angiotensin system, angiotensin II, plays a major role in cardiovascular regulation. In rats, both angiotensin receptor subtypes, AT₁ and AT₂, are up-regulated after myocardial infarction but previous studies failed to identify the cell types which express the AT₂ receptor in the heart. To address this question we established a single-cell reverse transcriptase-polymerase chain reaction for AT₁ and AT₂ receptors to determine whether these receptor subtypes are expressed in adult rat cardiomyocytes before and 1 day after myocardial infarction. By laser-assisted cell picking, section profiles of single cells without genomic DNA contamination were isolated. After dividing samples into two identical aliquots, polymerase chain reaction amplification for AT₁ and AT₂ receptors was carried out and polymerase chain reaction products were subjected to gel electrophoresis. Compared to control (n = 4) and sham-operated animals (n = 4), the number of cardiomyocytes expressing the AT₁ receptor mRNA 1 day after myocardial infarction (n = 4) was not changed (42% and 33% versus 45%, respectively). On the other hand, AT₂ receptor mRNA was expressed in 8% and 13%, respectively, of cardiomyocytes gained from control (n = 4) and sham-operated animals (n = 4) and in 14% isolated after myocardial infarction (n = 4). These results demonstrate for the first time that the AT₂ receptor is expressed in adult cardiomyocytes in vivo. They further suggest that the previously observed up-regulation of cardiac AT₁ and AT₂ receptors after myocardial infarction involves cell types other than cardiomyocytes.