Decreased modulation by endothelium of noradrenaline-induced contractions in aorta from stroke-prone spontaneously hypertensive rats.
Influences of endothelium on contractions of aortic ring preparations from 15 to 17 weeks old stroke-prone spontaneously hypertensive rats (SHRSP) and age-matched Wistar-Kyoto rats (WKY) were compared. Noradrenaline-induced contraction was potentiated by endothelium removal; the potentiation was greater in the WKY aorta. Noradrenaline (10(-5) M) induced a biphasic contraction in endothelium-intact WKY aorta, while endothelium-intact SHRSP aorta or endothelium-removed preparations of both strains showed a monophasic sustained contraction. The tension changes in high-K-induced contracture of the endothelium-intact preparation was less pronounced in both WKY and SHRSP aortae. The relaxation by acetylcholine (10(-5) M) of endothelium-intact aortae, precontracted with noradrenaline (5 X 10(-7) M), amounted to 78% in the WKY and to 44% in the SHRSP preparation. In endothelium-removed aortae, sodium nitroprusside induced a comparable relaxation in both WKY and SHRSP preparations. These results indicate that the endothelium plays an important role in controlling the noradrenaline-induced contraction and that the lower influence of endothelium in the SHRSP aorta is most likely due to a decreased activity of this endothelium.
Osugi
S
S
Research Institute of Hypertension, Kinki University, Osaka, Japan.
Shimamura
K
K
Sunano
S
S
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D002561:Cerebrovascular Disorders / Q000503:physiopathology*; D004558:Electric Stimulation; D004730:Endothelium, Vascular / Q000502:physiology*; D006973:Hypertension / Q000503:physiopathology*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009599:Nitroprusside / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
D009599:Nitroprusside; D000109:Acetylcholine; D009638:Norepinephrine