بررسی اثرات استرس مزمن شنا بر انقباض پذیری عضلات صاف آئورت مجزی و بدون اندوتلیوم در موش صحرائی نر

Stress can affect cardiovascular system and it&nbsp; is shown that&nbsp; can&nbsp; cause &nbsp;&nbsp; chronic hypertension. This study designed to test the effect of chronic stress &nbsp;&nbsp; on smooth muscle contractility of&nbsp; isolated aorta of rat . &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Male NMRI rats (180 - 320 g ) , were&nbsp;&nbsp; housed&nbsp; in&nbsp; defined&nbsp; conditions,12 h &nbsp;&nbsp; light / dark&nbsp; cycles ( 0700-1900 ) at 22&plusmn;20 C&nbsp; with&nbsp; free&nbsp; access&nbsp; to&nbsp; tap&nbsp; water &nbsp;&nbsp; and food. Chronic swimming (10 min) stress was induced , twice daily &nbsp;for 21 &nbsp;&nbsp; days .&nbsp; After&nbsp; 21&nbsp; days ,&nbsp; the&nbsp; animals&nbsp;&nbsp; were&nbsp;&nbsp; anesthetized&nbsp; with&nbsp; injection &nbsp;of &nbsp;&nbsp; thiopental(50 mg/kg ip),Blood samples were collected on Ethylenediamine &nbsp;&nbsp; tetracetic acid (EDTA). Adrenal&nbsp; glands&nbsp; were &nbsp;weighed and Red Blood Cell &nbsp;&nbsp; (RBC), Hematocrit (Hct)&nbsp; and&nbsp; Hemoglobin (Hb)&nbsp; tests&nbsp; were&nbsp; done. Thoracic &nbsp;&nbsp; aorta&nbsp; of&nbsp;&nbsp; test&nbsp;&nbsp; group&nbsp; (TG)&nbsp; and&nbsp; control&nbsp; group&nbsp; (CG)&nbsp; were&nbsp; removed&nbsp; and &nbsp;&nbsp; cleaned&nbsp; of connective tissue , and&nbsp; endothelium&nbsp; was denuded. A 5-6 mm &nbsp;&nbsp; ring of the tissue &nbsp;was&nbsp; mounted&nbsp; in a&nbsp; tissue&nbsp; bath and&nbsp; through&nbsp; an isometric &nbsp;&nbsp; transducer connected&nbsp; to&nbsp; a recorder. Tissue bath contained Krebs solution &nbsp;&nbsp; maitained at 37 &deg; C , and&nbsp; oxygenated&nbsp; with &nbsp;95%&nbsp; O2 , 5% CO2 . An &nbsp;original &nbsp;&nbsp; tension of 2.0 gr was applied and &nbsp;a&nbsp; 90&nbsp; min&nbsp; recovery&nbsp; period was allowed. &nbsp;&nbsp; After recovery&nbsp; period,&nbsp; KCl or&nbsp; Phenylephrine (Phe.)&nbsp; was&nbsp; added.&nbsp; Induced &nbsp;&nbsp; tension was recorded and calculated as g/mm2. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Results&nbsp;&nbsp;&nbsp; were&nbsp;&nbsp; compared&nbsp;&nbsp; using&nbsp; t-test&nbsp;&nbsp; and&nbsp;&nbsp; p<0.05&nbsp;&nbsp; was&nbsp;&nbsp; considered &nbsp;&nbsp;&nbsp; significant. Cortisol&nbsp;&nbsp; level&nbsp; in&nbsp; TG &nbsp;was significantly higher than CG (8.8&plusmn;0.05 &nbsp;&nbsp; ,2.4&plusmn;0.02 ng/ml respectively , p<0.0001).&nbsp; Ratio&nbsp; of&nbsp; adrenal glands mg/100g &nbsp;&nbsp; body&nbsp;&nbsp; weight&nbsp;&nbsp; in&nbsp;&nbsp;&nbsp; TG&nbsp;&nbsp; ( 13.29&plusmn;0.56 )&nbsp; was&nbsp;&nbsp; significantly&nbsp;&nbsp; higher &nbsp;&nbsp;than&nbsp;&nbsp; CG &nbsp;&nbsp; (10.26&plusmn;0.30). There&nbsp; were&nbsp;&nbsp; no&nbsp; significant&nbsp;&nbsp; differences&nbsp;&nbsp; in RBC , Hct&nbsp; and Hb &nbsp;&nbsp; between TG and CG. Concentrations of 20, 30 and 40&nbsp; mM of KCl induced &nbsp;&nbsp; higher&nbsp; tensions &nbsp;in TG&nbsp; significantly. Tensions&nbsp; induced by&nbsp; 100&nbsp; pM ,1,10 and &nbsp;&nbsp; 100 nM of Phe&nbsp; were lower in TG (p<0.05). &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; The results show that contractility of the&nbsp;&nbsp;&nbsp; smooth&nbsp; muscle&nbsp; from aorta of &nbsp;&nbsp; the chronically&nbsp; stress&nbsp; treated&nbsp; rats&nbsp; are&nbsp;&nbsp; different&nbsp;&nbsp; compared with controls. &nbsp;&nbsp; These&nbsp;&nbsp;&nbsp; changes&nbsp;&nbsp; in&nbsp;&nbsp; the&nbsp;&nbsp; contractility&nbsp; of&nbsp;&nbsp; the&nbsp;&nbsp; aorta&nbsp;&nbsp;&nbsp; could&nbsp;&nbsp; be&nbsp; due&nbsp; to &nbsp;&nbsp; disturbance&nbsp; in the calcium influx or its mobilization from intracellular pool .