Function of renal angiotensin AT2 receptors is not enhanced in Lyon hypertensive rats

1. Because we previously observed that angiotensin AT2 receptor stimulation decreased pressure-natriuresis, in the present study we examined the possible involvement of these receptors in altered sodium excretion shown by Lyon hypertensive (LH) rats. 2. In 9-week-old male anaesthetized LH rats and normotensive (LL) controls pretreated with an angiotensin-converting enzyme inhibitor (quinapril; 10 mg/kg) and an AT1 receptor antagonist (losartan; 10 mg/kg), angiotensin (Ang) II was infused (30 ng/kg per min) to stimulate AT2 receptors. In other groups of rats, an AT2 receptor antagonist (PD123319; 50 micro g/kg per min) was added before AngII infusion. 3. During AT2 receptor stimulation, LH differed from LL rats by significantly reduced renal blood flow (RBF), glomerular filtration rate and pressure diuresis and natriuresis. The addition of PD123319 did not change total RBF, whereas it did increase pressure diuresis and natriuresis in both strains. However, the effects of PD123319 were less marked in LH rats than in LL rats. 4. These findings confirm that, under the present experimental conditions, AT2 receptors are antinatriuretic and are not of greater functional importance in hypertensive animals of the Lyon strain.