Renal AT₁ receptor: Computerized quantification in spontaneously hypertensive rats and DOCA-salt rats

To assess the involvement of angiotensin II (Ang II) in the regulation of blood pressure, we investigated the alterations of renal Ang II type 1 (AT₁) receptors in two different models of hypertension; i.e., in spontaneously hypertensive rats (SHR) and deoxycorticosterone acetate (DOCA)- salt hypertensive rats by using the method for quantification of in vitro macroautoradiography (ARG). In the SHR model, although the number of cortical AT₁ receptors equaled that of Wistar Kyoto (WKY) rats at 4 and 12 weeks of age, the number of medullary AT₁ receptors in the 4-week-old SHR animals was significantly lower than that in age-matched WKY rats, and increased by 12 weeks of age. The renal AT₁ receptor number in DOCA-salt hypertensive rats was significantly higher than that in control rats. The amount of these receptors also increased with age in both DOCA-salt hypertensive rats and control rats. These findings indicate that the development of medullary. AT₁ receptors in early stages of hypertension in the SHR model differs from that in WKY rats or DOCA-salt hypertensive rats. This suggests that renal AT₁ receptors may contribute to the hypertension seen in the SHR group. The renal AT₁ receptors appear to be up-regulated in early stages of DOCA-salt- induced hypertension as well.