We investigated the haemodynamic parameters and the regulation of cardiac mRNA levels of the angiotensin receptor subtypes, AT1 and AT2, by the AT1-receptor antagonist losartan in rat heart during the acute phase of myocardial infarction. AT1- and AT2-receptor mRNA levels markedly increased at 30 minutes and peaked at 24 hours post myocardial infarction (12.6-fold increase for AT1- and 17.2-fold increase for AT2 compared with controls). Losartan significantly reduced mean blood pressure in sham-operated rats and decreased mean blood pressure and left ventricular end-diastolic pressure in myocardial infarction rats. However, the AT1- and AT2-receptor mRNA levels of losartan-treated rats showed a pattern similar to that of water-treated rats. The time-dependent increase of AT 1- and AT2receptor mRNA levels is associated with the early remodelling process of non-infarcted myocardium post MI and is independent of AT1-receptor blockade.
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