RENAL AGING CHANGE OF ALPHA(1)-ADRENOCEPTOR IN WISTAR RATS

1. The aging changes of density of the alpha(1)-adrenoceptors in the kidney were evaluated with Wistar rats of several ages (8, 52 and 104 weeks old). 2. [H-3]prazosin and [H-3]YM617 (newly synthesized alpha(1)-blocker) were used for the ligand. The B-max of [H-3]prazosin was 74.0 +/- 9.5 fmol/mg/protein in 8 week, 52.1 +/- 7.3 fmol/mg protein in 52 week, and 31.3 +/- 4.2 fmol/mg protein in 104 week rats, and that of [H-3]YM617 was 45.0 +/- 6.6 fmol/mg/protein in 8 week, 32.4 +/- 5.7 fmol/mg/protein in 52 week, and 19.3 +/- 5.5 fmol/mg/protein in 104 week rats. 3. The B-max of both ligands for 104 week rats was significantly decreased compared to 8 week rats, however, 52 week rats showed no decrease of B-max for both ligands. 4. The K-d values showed no difference in these three age groups for both ligands. 5. Autoradiographic study supported the result above mentioned. Furthermore, the binding sites of alpha(1)-adrenoceptors were mainly in the cortex (vascular wall and peritubular area) and that alpha(1)-adrenoceptors were chiefly chlorethylclonidine dihydrochloride (CEC) insensitive.