Increased Angiotensin II Receptors in Neuronal Cultures from Hypertensive Rat Brain

Binding of 125I-angiotensin II (ANG II) to neuronal cultures made from the brains of 1-day-old normotensive (Wistar-Kyoto, WKY) and spontaneously hypertensive (SH) rats was time dependent, saturable, reversible, and 90-95% specific. Neuronal cultures from SH rats bound 50-70% more 125I-ANG II compared with their WKY controls. Scatchard analysis revealed that the increase in the specific binding of ANG II to SH rat neuronal cultures was due to an increase in the number of binding sites per cell rather than change in the affinity of receptors for ANG II. Light-microscopic autoradiographic analysis showed that ANG II specific binding sites were located on neuronal cell bodies and neurites. Treatment of neuronal cultures from both strains of rats with alpha-methyl-p-tyrosine caused a 50-60% decrease in the endogenous levels of norepinephrine (NE) and dopamine (DA). This decrease was associated with increases in the specific binding of 125I-ANG II in neuronal cultures from WKY rat brain. In contrast, ANG II binding in neuronal cultures from SH rat brain failed to respond to changes in NE and DA levels. These observations suggest that ANG II specific receptors are increased and that they are not under a negative-feedback control by catecholamines in SH rat brain neuronal cultures.