Cardiac Expression of Sarcolipin Calpain After Immobilization Stress in Young Old Female Rats, Role of Alpha Beta Adrenoceptor Blockers

Stress cardiomyopathy has aroused interest in the cardiology community. Immobilization stress test ,a model of emotional stress in rats, can be used to study the molecular mechanism of this syndrome. The aim of this study was to investigate the effect of immobilization stress on cardiac expression of sarcolipin and calpain in addition to myocardial performance and its relation to serum catecholamines. 72 female albino rats were included in the present study and were classified into 2 categories of young (Y) and old (O) female rats. Each category was divided into 3 groups of 12 animals each: control group (CG), Immobilization stress (IMO) group: female rats subjected to immobilization stress for 30 min, immobilization after adrenoceptor blockers AB (IMO+AB) group: female rats subjected to immobilization stress for 30 min after receiving a adrenergic blocker, Regitamine (2.5 mg/kg i.p) p adrenergic blockers Inderal (2.5 mg/kg i.p) . Thus , 6 groups were included in the present study, 3 young groups 3 old groups. At the end of experimental protocol, cardiac performance, serum catecholamines and cardiac expression of sarcolipin SLN calpain were measured. The results showed that epinephrine E norepinephrine NE increased significantly (p 0.05) in IMO IMO+AB groups in Y O female rats compared to corresponding values in CG. Regarding cardiac performance, there was a significant decrease (p 0.05) in contractility index dp/dt in IMO groups (Y O) compared to control groups. The effect of IMO on cardiac expression of SLN showed a significant decrease (p 0.05) in SLN of atria a significant increase (p 0.05) in SLN of ventricles in young old rats compared to CG. Administration of AB resulted in significantly increased (p 0.05) SLN of atria in O rats making them approaching the control values. significantly decreased SLN of ventricles in Y O groups compared to IMO. cardiac expression of calpain increased significantly (p 0.05) in O rats compared to young rats and in IMO IMO+AB groups compared to control values in young rats. No significant change was found in IMO IMO after AB compared to CG in old rats. We concluded that the increased ventricular expression of sarcolipin might be caused by supra physiological levels of catecholamines which stimulate adrenoceptors and alter expression of calcium regulatory protein genes. The difference in expression of calcium regulatory protein genes between young and old rats may explain the increased incidence of stress cardiomyopathy in old females.