TY - JOUR T1 - The Effect of Chronic Swimming Stress on Smooth Muscle Contractility in the Isolated Endothelium Denuded Aorta of Male Rat TT - بررسی اثرات استرس مزمن شنا بر انقباض پذیری عضلات صاف آئورت مجزی و بدون اندوتلیوم در موش صحرائی نر JF - umsha JO - umsha VL - 7 IS - 4 UR - http://sjh.umsha.ac.ir/article-1-901-en.html Y1 - 2001 SP - 0 EP - 0 KW - Aorta/ Hydrocortisone/ Muscle KW - Contraction/ Rats/ Stress N2 - Stress can affect cardiovascular system and it is shown that can cause chronic hypertension. This study designed to test the effect of chronic stress on smooth muscle contractility of isolated aorta of rat . Male NMRI rats (180 - 320 g ) , were housed in defined conditions,12 h light / dark cycles ( 0700-1900 ) at 22±20 C with free access to tap water and food. Chronic swimming (10 min) stress was induced , twice daily for 21 days . After 21 days , the animals were anesthetized with injection of thiopental(50 mg/kg ip),Blood samples were collected on Ethylenediamine tetracetic acid (EDTA). Adrenal glands were weighed and Red Blood Cell (RBC), Hematocrit (Hct) and Hemoglobin (Hb) tests were done. Thoracic aorta of test group (TG) and control group (CG) were removed and cleaned of connective tissue , and endothelium was denuded. A 5-6 mm ring of the tissue was mounted in a tissue bath and through an isometric transducer connected to a recorder. Tissue bath contained Krebs solution maitained at 37 ° C , and oxygenated with 95% O2 , 5% CO2 . An original tension of 2.0 gr was applied and a 90 min recovery period was allowed. After recovery period, KCl or Phenylephrine (Phe.) was added. Induced tension was recorded and calculated as g/mm2. Results were compared using t-test and p<0.05 was considered significant. Cortisol level in TG was significantly higher than CG (8.8±0.05 ,2.4±0.02 ng/ml respectively , p<0.0001). Ratio of adrenal glands mg/100g body weight in TG ( 13.29±0.56 ) was significantly higher than CG (10.26±0.30). There were no significant differences in RBC , Hct and Hb between TG and CG. Concentrations of 20, 30 and 40 mM of KCl induced higher tensions in TG significantly. Tensions induced by 100 pM ,1,10 and 100 nM of Phe were lower in TG (p<0.05). The results show that contractility of the smooth muscle from aorta of the chronically stress treated rats are different compared with controls. These changes in the contractility of the aorta could be due to disturbance in the calcium influx or its mobilization from intracellular pool . M3 ER -