Korean J Nephrol.  1999 Nov;18(6):887-893.

The Studies of Contractile and Relaxing Responses of Abdominal Aorta and Effects of Angiotensin II Blocker(Losartan) in Spontaneously Hypertensive Rats Combined with Renovascular Hypertension

• Lee HJ
• Han BK
• Lee EY
• Kim JS
• Gal EH
• Kim MH
• Kim JM
• Song KH
• Choi SO

Abstract

This study was designed to evaluate the contractile and relaxing responses of abdominal aorta in renovascular hypertension accompanied with essential hyper- tension and to examine the effect of angiotensin II receptor blocker(losartan). An experimental renovascular hypertension accompanied with essential hypertension model was established by clipping the left renal artery of spontaneously hypertensive rats(SHR). These rats were then divided into two groups of which one was given losartan during the one week postopertion before being terminated. Ring preparations of the abdominal aorta were obtained one week after the operation. The contraction of abdominal aorta strips were induced by high potassium or norepinephrine, and relaxation produced by acetylcholine or sodium nitroprusside. The contractile and relaxing responses were recorded and compared with data obtained from the control group. In the second experiment, the rats received angiotensin Il blocker(LRAO group), losartan in the drinking water for 7 days after the induction of the renal artery stenosis operation. Then, the contractile and relaxing responses were evaluated by the same method. The following results were obtained; 1) The contractile responses to the high level potassium solution and norepinephrine in renal artery occlusion(RAO) group were significantly increased compared with SHR group(p<0.05). 2) The contractile reponses to the high level norepinephrine in LRAO group were similar to that of SHR control group. However, there was no remarkable differences for high potassium. 3) The relaxing responses to the acetylcholine were significantly reduced in the RAO group compared with the SHR group. However, there was no remarkable differences for sodium nitroprusside. 4) There were no significant differences in the acetylcholine or sodium nitroprusside induced vasodilation response between the LRAO group and SHR group. From the above result, it is suggested that re- novascular hypertension in spontaneously hypertensive rats might induce changes of vascular responses and this effects may be concerned with endothelium-dependant mechanism. And angiotensin II receptor blocker rnay prevent the development of abnormal endothelium-dependent relaxation in renovascular hypertension accompanied with essential hypertension by maintaining endothelial function.

MeSH Terms

Acetylcholine
Angiotensin II*
Angiotensins*
Animals
Aorta, Abdominal*
Drinking Water
Hypertension
Hypertension, Renovascular*
Losartan
Nitroprusside
Norepinephrine
Potassium
Rats
Rats, Inbred SHR*
Receptors, Angiotensin
Relaxation
Renal Artery
Renal Artery Obstruction
Vasodilation
Acetylcholine
Angiotensin II
Angiotensins
Drinking Water
Losartan
Nitroprusside
Norepinephrine
Potassium
Receptors, Angiotensin