Cardiac angiotensin II receptor populations during aortocaval fistulae, AII and beta adrenergic receptor blockade

Cardiac angiotensin (AII) receptor subtype expression that occurs during volume overload and beta adrenergic blockade was assessed in male rats pretreated with saline (S) or saralasin (Sar) for 2 weeks. Following pre-treatment, an arteriovenous fistula was produced and some animals were then infused with metoprolol or propranolol for 28 days after which AII binding studies were done. In sham-operated animals, there was more of the AT1 receptor subtype that exhibited more monophasic binding. With fistula, there was biphasic binding, with the AT2 population being the predominate type. Metoprolol or propranolol partially reversed the receptor population shift back to AT1, indicating that the AT2 receptor subtype may play a role in the heart enlargement induced by volume overload and suggesting a functional interrelationship between the beta adrenergic receptors and AII receptors.