Angiotensin II receptor binding in the locus ceruleus of spontaneously hypertensive rats and Wistar-Kyoto rats: a quantitative autoradiographic study with references to hypertension and cardiac/testicular hypertrophy.

The locus ceruleus (LC) contains a high density of angiotensin II (AII) receptors. The role of AII receptors at the LC in genetic hypertension and organ function is unclear. Spontaneously hypertensive (SHR) rats and Wistar-Kyoto (WKY) rats were studied, and blood pressure of animals was measured using the tail-cuff method. Animals were decapitated and the heart weight (HW) and testicular weight (TW) of animals measured. AII receptor binding was carried out by incubating the LC tissue sections with 200 pM [(125)I]-AII receptor ligand, and measured using quantitative autoradiography. Results showed that the HW/BW ratio was significantly higher in SHR rats than WKY rats. However, the TW/BW ratio was higher in SHR rats than WKY rats only at two hypertensive stages, whereas AII receptor binding capacity in the LC was also statistically higher in SHR rats than WKY rats. Results indicated that cardiac and testicular hypertrophies were related to higher AII receptor binding in the LC of SHR rats, when compared with WKY rats. Interestingly, the literature shows that there is an LC-testes axis. In conclusion, this study indicated that AII receptors in the LC are associated with genetic hypertension, and testicular weight could be a reasonable index for essential hypertension.