Angiotensin II and aldosterone receptor binding in rat heart and kidney: response to chronic angiotensin II or aldosterone administration.

Angiotensin II (AII) and mineralocorticoid receptors (MRs) have been identified in the mammalian heart and kidney. Their response to chronic elevations in circulating AII or aldosterone (ALDO) (or both) is unknown in either primary or secondary hyperaldosteronism. Nonendothelial angiotensin-converting enzyme (ACE) activity has been found in the fibrous tissue response that involves intramyocardial coronary arteries and microscopic scarring. Whether this tissue ACE could affect AII receptors and MRs in the area of myocardial fibrosis is likewise unknown. To address these questions, we monitored AII and MR binding in the rat heart and kidney after chronic AII or ALDO infusion. All receptor and MR binding were localized by in vitro autoradiography with 125I-[Sar1, Ile8]-labeled AII and [1,2,6,7 3H]-labeled ALDO, respectively. To characterize AII receptor subtypes, a type I antagonist (DuP753) or type II antagonist (PD 123177) was used. Four experimental groups were examined: unoperated, untreated, age- and sex-matched controls; age- and sex-matched uninephrectomized control rats receiving a high sodium diet; animals that received AII (9 micrograms/hr sc) for 2, 4, 6, or 8 weeks; and uninephrectomized rats on a high sodium diet that received ALDO (0.75 microgram/hr sc) for similar periods of time.(ABSTRACT TRUNCATED AT 250 WORDS)