The rat thoracic aorta was harvested to determine whether either hyperkalemia or hypothermia impairs the endothelium-dependent relaxation of the vascular smooth muscle. Isolated thoracic aorta segments were studied in five groups(n=10 in each
group). In
group I(control), the isolated aortic segments were suspended in organ bath without any intervention. In group II(endotheilum removal), the endothelium of the aortic segment was removed by gentle rubbing of the intimal surface with a pair of
forceps. In
group III(4ST), IV(4mST), and V(37ST), the aortic segments were exposed for 45minutes to 4℃ St. Thomas' hospital cardioplegic solution(ST:NaCl, 144.3; KCl, 19.6; MgCl2, 15.7; CaCl, 2.2 mmol/L, 4℃ modified St. Thomas' hospital cardioplegic
solution(NaCl, 144.3; KCl, 140.0; MgCl2, 15.7; CaCl2, 2.2 mmol/L), and 37℃ ST, before suspending in the organ bath, respectively, Then, aorta segments were suspended in organ baths(physiologic salt solution, 37℃, 95% oxygen and 5% carbon
dioxide)
for
isometric tension recording.
The vasodilatation to acetylcholine (10-9 to wo 10-5 mol/L) was not impaired in control, 4ST, 4mST, and 37ST groups. The vasodilatation to acetylcholine was impaired in endothelium removal group. The vasodilatation to sodium nitroprusside (10 7-9
to 10
7-6 mol/L) was not impaired in all groups.
In conclusion, both hyperkalemia and hypothermia do not alter irreversibly the function of the endothelium of the thoracic aorta of the rat.
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