Hypertensive left ventricular hypertrophy: relation to beta-adrenergic receptor kinase-1 (betaARK1) in peripheral lymphocytes.

BACKGROUND

Left ventricular hypertrophy (LVH) is associated with increased cardiovascular risk and altered sympathetic regulation in hypertension.

OBJECTIVES

To determine whether the level of beta-adrenergic receptor kinase-1 (betaARK1) in lymphocytes is related to LVH in patients with hypertension.

METHODS

Forty-nine patients with untreated essential hypertension were recruited to the study and classified into two groups: left ventricular hypertrophy (LVH: left ventricular mass index > or =134 g/m in men and > or =110 g/m in women; ages 52.4 +/- 12.8 years, n = 25) and non-LVH (NLVH: left ventricular mass index < 134 g/m in men and < 110 g/m in women; ages 50.8 +/- 13.1 years, n = 24). Lymphocytes were isolated from patients and quantitative-competitive reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoblotting were used to estimate the expression of betaARK1 in the lymphocytes. G-protein-coupled receptor kinase activity was assessed by rhodopsin phosphorylation assay.

RESULTS

The expression of betaARK1 in lymphocytes was greater in the LVH group than in the NLVH group (0.0069 +/- 0.002 ng compared with 0.0048 +/- 0.0017 ng, P < 0.01) and correlated well with left ventricular mass index (r = 0.527, P < 0.001) and relative wall thickness (r = 0.627, P < 0.001). The concentration of betaARK1 protein in lymphocytes from individuals with LVH was increased two-fold compared with that in the NLVH group (both n = 7). Lymphocyte G-protein-coupled receptor kinase activity from LVH was enhanced 1.7-fold compared with NLVH (1.03 +/- 2.16 and 1.79 +/- 1.87 pmol phosphate/min per mg protein, respectively; P < 0.05, n = 7 for each group).

CONCLUSIONS

The concentration of betaARK1 in lymphocytes is greater in hypertensive individuals with LVH than in those without LVH and parallels the degree of hypertrophy. Generalized alterations in beta-adrenergic signalling, including betaARK1, could be a major contributory factor in the development of LVH in hypertension, and the concentration of betaARK1 in lymphocytes can reflect the development of LVH in a patient with hypertension.