The Effect Of Exogenous Apelin On The Cardiomyocyte Hypertrophy

Objective: Cardiac hypertrophy is an independent risk factor for augmented mortality of cardiovascular diseases. Recent studies show that in the hypertrophic myocardium, apelin, the endogenous ligand for the orphan G-protein-coupled receptor APJ, decreases. We then hypothesize that there may exist some relation between the levels of apelin and cardiac hypertrophy. The purpose of this experiment is to examine the effect of exogenous apelin on angiotensin â…¡ (ang â…¡ )-induced cardiomyocyte hypertrophy and explore its possible mechanism.Methods: Neonatal cardiomyocytes of SD rats were cultured in vitro.Immunocytochemistry was used to identify cardiomyocytes. Then the studywas performed according to the different groups(1)control; (2) ang â…¡(10^-7mol/l); (3)apelin-13 (10^-6mol/l); (4) ang â…¡ (10^-7mol/l) +apelin-13(10^-8mol/l); (5) ang â…¡ (10^-7mol/l) +apelin-13 (10^-7mol/l); (6) ang â…¡(10^-7mol/l)+apelin-13( 10^-6mol/l).Five days after pretreatment, the followingindexes are measured. The surface area and diameter of myocyts wereobserved by Image-Pro Plus. Contents of cellular protein content and nitricoxide (NO) in the culture solution were measured.Results: Immnocytochemistry staining confirmed cardiomyocytes with purity higher than 90%,indicating a good isolation of cardiomyocytes .Ang â…¡ 10^-7mol/l alone caused obvious increases in the diameter, surface area and protein content of myocyts ( P<0.01 ) , however,co-administration ofapelin(10"6mol/l) inhibited ang II-induced increases in cell size and protein content(P<0.05). In addition, ang II 10"7mol/l alone caused a decreased amount of NO in the culture solution ( PO.01 ) ,but co-administration of apelhXlO^mol/l) lead to increased amount of NO compared with ang II alone(P<0.05). Correlation analysis shows the content of NO in the culture solution has a negative correlation with the above three hypertrophic indexes respectively (R=-0.623, PO.01; R=-0.731, PO.01; R=-0.584, PO.01).Conclusion: Apelin could attenuate angiotensin II -induced cardiomyocyte hypertrophy ."Nitric oxide seemed to play a role in this antihypertropic process.