Influence of the endothelium on vascular responses of aortae from endotoxic rats
Wakabayashi, I.; Hatake, K.; Kakishita, E.; Hishida, S.
Journal of Pharmacy and Pharmacology 42(7): 477-480
1990
ISSN/ISBN: 0022-3573 PMID: 1980287 Document Number: 355900
Intraperitoneal injection of endotoxin diminished the in-vitro contractile response of rat aorta to phenylephrine or clonidine, whether the intimal layer was disrupted or not. The relaxing responses to acetylcholine and sodium nitroprusside in aorta precontracted with 10-6 M phenylephrine were similar between control and endotoxic groups. However, when the precontractile force following phenylephrine was adjusted to a equivalent level, the relaxing responses to acetylcholine and sodium nitroprusside were diminished in the endotoxic aorta compared with the controls. There was no significantly differences between the two groups in the increase in cyclic GMP levels induced by acetylcholine or by sodium nitroprusside. These results suggest that aortae from endotoxic rats show decrease responsiveness to .alpha.-adrenoceptor stimulation not because of enhancement of the endothelium-derived relaxing factor but because of abnormality in the vascular smooth muscle which is not specific for subtypes of the .alpha.-adrenoceptor.