Expression of Angiotensin AT1 and AT2 Receptors in Adult Rat Cardiomyocytes after Myocardial Infarction

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.