G-protein-coupled receptor kinase expression in hypertension

In human hypertension we have recently identified an increase in lymphocyte G-protein receptor kinase-2 (GRK-2) protein expression, the key protein regulating the interaction between G-protein-coupled receptors and activation of adenylyl cyclase. However, it was not known whether this increase in GRK-2 protein expression was attributable to regulation at the level of translation. Furthermore, the relationship between extent of GRK-2 expression, receptor activation of adenylyl cyclase, and blood pressure was unclear. We therefore studied lymphocytes from 7 young subjects with borderline hypertension and 14 young normotensive subjects. Immunodetectable GRK-2 protein expression in lymphocytes from subjects with hypertension was increased (155%+/-7% of normotensive subjects; P < .05). In addition, GRK-2 protein expression was positively correlated with blood pressure (r = 0.53; P = .013) and inversely correlated with beta-adrenergic-mediated adenylyl cyclase activity (r = -0.54, P = .012). However, lymphocyte GRK-2 messenger ribonucleic acid (mRNA) content was not altered (110%+/-13% of that observed in normotensive control subjects). Increased GRK-2 protein expression may be an important factor in the impairment of beta-adrenergic-mediated vasodilation, characteristic of the hypertensive state.