[Angiotensin II induced myocardial hypertrophy in neonatal rats could be attenuated by activated κ-opioid receptor via modulating the calcineurin signal pathways].
OBJECTIVE
To observe the effect of κ-opioid receptor (κ-OR) stimulation on Angiotensin II (Ang II)-induced cardiomyocyte hypertrophy in vitro cultured myocardial cells from neonatal rats and on calcineurin (CaN) signal pathways.


METHODS
Cultured myocardial cells of neonatal rats were divided into control group, CSA (1 µmol/L) group, Ang II (1 µmol/L) group, Ang II (1 µmol/L) + U50488H (1 µmol/L) group, Ang II (1 µmol/L) + CSA (1 µmol/L) group, Ang II (1 µmol/L) + Rp-cAMPS (1 µmol/L) group, Ang II (1 µmol/L) + CSA (1 µmol/L) + U50488H (1 µmol/L) group and Ang II (1 µmol/L) + PTX5 mg/L + U50488H (1 µmol/L) group. The hypertrophic myocytes were induced by Ang II 1µmol/L before κ-OR agonist U50488H 1 µmol/L was administered. The antihypertrophic effect of κ-OR stimulation was observed in the presence of ciclosporine A (CsA) 1 µmol/L, cAMP triethyl-ammonium salt (Rp-cAMPS) 1 µmol/L, and pertussistoxin ( PTX) 5 mg/L. The total protein content was assayed by the method of Lowry. The [Ca²⁺]i was measured by confocal microscope using Fluo-3/AM as flouresecent indicator. The relative expression of CaN was determined by Western blot.


RESULTS
(1) The total protein content of Ang II group was significantly higher than that in control group (P<0.01), which could be equally reduced by cotreatment with U50488H, CSA and Rp-cAMPS (P<0.01). Total protein content of the Ang II + PTX + U50488H group and the Ang II group was similar. (2) The [Ca²⁺]i was significantly higher in Ang II group of neonatal rat cardiomyocytes than that in control group (P<0.01), which could be reduced by cotreatment with U50488H, CSA and Rp-cAMPS (P<0.01). [Ca(2+)]i was similar between the Ang II + PTX + U50488H group and the Ang II group. (3) The expression of CaN was significantly higher in Ang II group than that in control group (P<0.01), which could be significantly reduced by cotreatment with U50488H, CSA and Rp-cAMPS (P<0.01). CaN was similar between the Ang II + PTX + U50488H group and the Ang II group.


CONCLUSIONS
κ-opioid receptor activation could attenuate Ang II induced cardiomyocytes hypertrophy via reducing [Ca²⁺]i and downreglating CaN.
Pharmacy Department of Second Affiliated Hospital of Zhengzhou University, Zhengzhou 450014, China.
Ling
L
Xing
Pharmacy Department of Second Affiliated Hospital of Zhengzhou University, Zhengzhou 450014, China; Email: xclzy@126.com.
Zhiye
Z
Li
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D000804:Angiotensin II; D000814:Aniline Compounds; D000818:Animals; D000831:Animals, Newborn; D019703:Calcineurin; D002478:Cells, Cultured; D006984:Hypertrophy; D009206:Myocardium; D032383:Myocytes, Cardiac; D051381:Rats; D017473:Receptors, Opioid, kappa; D015398:Signal Transduction; D014966:Xanthenes
D000814:Aniline Compounds; D017473:Receptors, Opioid, kappa; D014966:Xanthenes; C116587:kappa(1) opioid receptor; D000804:Angiotensin II; C059715:Fluo-3; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D019703:Calcineurin