High salt intake differentially regulates kidney angiotensin IV AT₄ receptors in Wistar-Kyoto and spontaneously hypertensive rats

Functional angiotensin IV (Ang IV) receptors (denoted AT₄) are localized to the outer stripe of the medulla in the rat kidney, and may play a critical role in salt homeostasis. The purpose of this study was to determine if AT₄ receptor binding in the kidney is differently regulated in the salt-sensitive spontaneously hypertensive (SH) rat compared to Wistar Kyoto (WKY) controls. AT₄ receptor binding was determined using in vitro receptor autoradiography. AT₄ receptor binding in the outer stripe of the medulla was similar in WKY and SH rats maintained on a 1% salt diet. A high salt diet (8%) resulted in a statistically significant increase (28%) in AT₄ receptor binding in kidneys from WKY rats. However, there was no change in AT₄ receptor binding in the kidneys of SH rats fed the same diet. The present data indicate that AT₄ binding sites are regulated by salt intake. In addition, regulation of this receptor may be impaired in the kidneys of SH rats, explaining in part the salt-sensitivity of this strain.