DOPAMINE D-3 RECEPTOR IN PERIPHERAL MONONUCLEAR-CELLS OF ESSENTIAL HYPERTENSIVES

Dopamine D-3 receptor was studied in peripheral mononuclear cells of h igh-normal, stage 1, stage 2, and stage 3 essential hypertensives usin g a radioligand binding assay technique with [H-3]-7-hydroxy-N,N-di-n- propyl-2-aminotetraline (7-OH-DPAT) as a radioligand. A group of de no vo Parkinsonian patients was also examined as a reference group of imp aired dopaminergic function. [H-3]-7-OH-DPAT was bound specifically to human peripheral mononuclear cells in a manner consistent with the la beling of a dopamine D-3 receptor. No changes in free dopamine, norepi nephrine, epinephrine and aldosterone levels, renin activity, dissocia tion constant of [H-3]-7-OH-DPAT binding, or the pharmacological profi le of [H-3]7-OH-DPAT binding were found between normotensive control s ubjects and essential hypertensives or Parkinsonians. The density of p eripheral mononuclear cell [H-3]-7-OH-DPAT binding sites increased in essential hypertensives parallel to blood pressure value augmentation. A higher density of [H-3]-7-OH-DPAT binding sites was found in Parkin sonians. In these patients, the density of [H-3]-7-OH-DPAT binding sit es was similar to that observed in high-normal subjects and in stage 1 essential hypertensives. The increased density of peripheral mononucl ear cell dopamine D-3 receptor in hypertension as well as in Parkinson 's disease may represent an upregulation mechanism consequent to impai red dopaminergic function. In view of the difficulty in identifying ma rkers of peripheral dopamine function, analysis of dopamine D-3 recept or in peripheral mononuclear cells may help evaluate whether the dopam inergic system is involved in hypertension.