Volume 7, Number 4 (Scientific Journal of Hamadan University of Medical Sciences-Winter 2001)                   Sci J Hamadan Univ Med Sci 2001, 7(4): 0-0 | Back to browse issues page

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Malakoti M, Zahedi Asl S. The Effect of Chronic Swimming Stress on Smooth Muscle Contractility in the Isolated Endothelium Denuded Aorta of Male Rat. Sci J Hamadan Univ Med Sci . 2001; 7 (4)
URL: http://sjh.umsha.ac.ir/article-1-901-en.html

Abstract:   (632 Views)

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 .

Type of Study: Original | Subject: Special

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