Abstract
we studied the number and affinity of catecholamine receptos in SD rat kidney by radioreceptor technique.
The following conclusions were obtained:
1) By using 3H-prazosin, the numbers of α1-receptor (Bmax) in rat renal cortex were greater than those in rat kidney medulla. As for affinity (Kd), the significance was not recognized between the two. Bmax of the rat renal cortex to 3H-prazosin binding was 96.1fmol/mg protein, and Kd was 0.17nM, and for the rat renal medullar these values were 44.5fmol/mg protein and 0.13nM, respectively.
2) By measurement of D1-receptor using 3H-SKF38393 in the rat renal cortex in the Scatchard plot analysis, positive cooperativity was observed under the low concentration of hot ligand which was less than 1nM. But at the concentration of hot ligand over 1nM, the plots showed a straight line. Bmax of the rat renal cortex to 3H-SKF38393 was 2.5pmol/mg protein and Kd was 5.3nM.
3) Based on displacement by dopamine for 3H-prazosin binding to rat renal cortex, it was surmised that high concentration of dopamine had an affinity to α1-adrenoceptors.
4) There was no change in the Kd and Bmax of α1-receptor in the rat renal cortex after incubation of samples with low concentration of dopamin. However, in the case of hih concentration of dopamine, a remarkable decrease of the affinity (Kd) of α1-adrenoceptor was observed.
