Dopamine D₅ Receptor Expression is Unchanged in Peripheral Blood Lymphocytes in Essential Hypertension

Abstract

The present study was designed to investigate possible changes in the expression of lymphocyte dopamine receptor in essential hypertension. The expression of dopamine D₅ receptor was evaluated by radioligand binding techniques using [³H]-SCH 23390 as ligand. Plasma catecholamines, aldosterone levels and plasma renin activity were also measured.

Eleven borderline hypertensive patients, 15 patients with mild essential hypertension, 7 patients with moderate essential hypertension and 5 patients with severe essential hypertension were examined. Plasma catecholamine levels were assayed by high pressure liquid chromatography with electrochemical detection. Dopamine D₅ receptor was measured by radioligand binding techniques. Plasma aldosterone levels and renin activity were determined by radio immunoassay.

[³H]-SCH 23390 was specifically bound to human peripheral blood lymphocytes. The binding was time-, temperature- and concentration- dependent with a dissociation constant (Kd) value of 0.59 nM and a maximum density of binding sites (Bmax) of 223 pmol/ 10⁶ cells.

Dopamine competed with [3H]-SCH 23390 binding in the submicromolar range suggestin the labelling of a dopamine D5 receptor. No changes in peripheral blood lymphocytes between essential hypertensive patients and normotensive subjects. Also catecholamines, plasma renin activity and aldosterone levels were unchanged.

In spite of the availability of a sensitive technique for measuring dopamine receptors in human peripheral lymphocytes, no change in their expression was noticeable in essential hypertension. This suggests that dopamine receptor analysis in essential hypertension is not a useful marker for investigating hypertension-dependent changes of the peripheral dopaminergic system. the density of [9 HI-SCH 23390 binding sites were observed in human

Key Words:

• Essential hypertension
• dopamine receptors
• radioligand binding
• D₅ receptor
• [³H]-SCH 23390