Effects of losartan on haemodynamic parameters and angiotensin receptor mRNA levels in rat heart after myocardial infarction.

We investigated the haemodynamic parameters and the regulation of cardiac mRNA levels of the angiotensin receptor subtypes, AT1 and AT2, by the AT,-receptor antagonist losartan in rat heart during the acute phase of myocardial infarction. AT1- andAT2-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 AT,- andAT2-receptor mRNA levels of losartan-treated rats showed a pattern similar to that of water-treated rats. The time-dependent increase of AT1- and AT2-receptor mRNA levels is associated with the early remodelling process of non-infarcted myocardium post MI and is independent of AT1-receptor blockade.