[3H]Yohimbine Binding Studies

The autoradiographic localization of a l- and az-adrenoceptors was identified in 22-week-old Wistar- Kyoto rat kidney, using al-selective (pH]bunazosin) and az-selective (PH]yohimbine) antagonists. pH]Bunazosin binding was distributed predominantly over the cor-tex, less over the outer medulla and was absent from the inner medulla. [3H]Yohimbine binding was distributed predominantly over the med-ulla, less over the renal cortex and was absent from the inner medulla. In addition, the distribution of renal a-adrenoceptors was investigated in 3-, 7- and 22-week-old spontaneously hypertensive rats (SHRs) using a computerized image analysis system. Renal a-adrenoceptors were both found to be increased in SHRs at all ages tested compared with their respective controls and were increased in both the cortex and the outer medulla. The increase in renal o-adrenoceptors was already present in 3-week-old SHRs whose systolic blood pressures did Received for publication I May 1990; accepted 1