Aim To demonstrate the effects and mechanism of adenosine A1 receptor agonist R(-)-N6-(2-phenylisopropyl) adenosine(R-PIA) on high glucose(HG)-induced myocardial hypertrophy by in vitro cultured myocardial cells from neonatal rats.Methods The protein content was assayed by the method of Lowry. The expression of p-ERK1/2 and ERK1/2 was determined by Western blot.The [Ca~(2+)]I transient changes of cell loaded Fura-2/AM were measured by Till image system.Results 1 μmol·L~(-1) R-PIA and U0126 inhibited similarly HG-induced increase of the protein content and [Ca~(2+)]I transient along with the relative expression of p-ERK1/2.These responses were completely abolished by adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine(CPDPX).Conclusion Adenosine A1 receptor stimulation significantly inhibits HG-induced myocardial hypertrophy by mediating ERK1/2 pathway and Ca~(2+).