Beta₂-adrenoceptor density on membranes and on intact mononuclear cells in essential hypertension

Summary

Alterations in the status or in the regulation of adrenoceptors may contribute to essential hypertension. This could be studied using the recently introduced radio-ligand binding techniques to characterize the adrenoceptors on human peripheral blood cells.

The present study shows that patients with essential hypertension have a twofold increase ofβ ₂-adrenoceptor density onintact mononuclear cells as compared to normotensive controls: 859±260 (n=10) vs. 420±119 (n=10) maximal binding sites for (±) 125-Iodocyanopindolol expressed as molecules per cell (P<0.001). Furthermore, there is a highly significant correlation (r=0.86) between the calculated mean arterial blood pressure and theβ ₂-adrenoceptor density over a wide range of normal and increased blood pressure.

These findings could only be demonstrated with intact mononuclear cells but not with membrane fractions. No difference was found in receptor affinity between patients with essential hypertension and normotensive controls.

Thus, essential hypertension is combined with a higherβ ₂-adrenoceptor density on intact mononuclear cells which might represent, for example, an increased density of prejunctionalβ ₂-adrenoceptors. Mean arterial blood pressure is positively correlated withβ ₂-adrenoceptor density over a wide range of blood pressure in normotensives and hypertensives. The expression ofβ ₂-binding sites on the cell surface is possibly altered in essential hypertension resulting in a disparity between intracellular and extracellular binding sites as compared with normotensives.