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.
tension was recorded and calculated as g/mm2.
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 .
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