Instructions for use Title Chronic beta-adrenergic receptor stimulation enhances the expression of G-Protein coupled receptor kinases , GRK 2 and GRK 5 , in both the heart and peripheral lymphocytes

Enhanced expression of G-protein coupled receptor kinase (GRK) was reported in failing hearts. In this study, we aimed to clarify the stability of enhanced GRK mRNA expression, and to examine the correlation between the expression level of GRK mRNA in peripheral lymphocytes and that in hearts. Isoproterenol was injected into rats for 2 weeks, and then GRK5 mRNA was assessed by quantitative RT-PCR. An enhanced expression of cardiac GRK5 mRNA was observed even after four weeks of recovery period. Isoproterenol-induced increase of GRK2 and GRK5 mRNA expression was equally observed both in hearts and lymphocytes, and there was a close correlation in the level of each GRK mRNA expression between heart and lymphocyte. These results suggested that GRK mRNA level was maintained at high level for a long period without continuous β-adrenergic receptor stimulation, and that GRK level of circulating lymphocytes could be used as a surrogate marker to estimate the level of cardiac GRK expression, and presumably β-adrenergic receptor function of cardiomyocytes.