Effects of endothelial cell removal on constrictor and dilator responses of aortae of pregnant rats.
1. The possibility has been examined that changes in sensitivity of the aorta occurring during pregnancy in the rat are due to changes in output of endothelium-derived relaxing factor (EDRF). 2. Concentration-isometric response curves, obtained in vitro, from thoracic aortic rings of non-pregnant rats in oestrous and 20-day pregnant rats to noradrenaline (NA) and phenylephrine (PE) were shallower with lower maxima when compared to those obtained to the thromboxane A2-mimetic U46619. 3. Removal of endothelium from aortae of non-pregnant animals caused significant shifts to the left of the curves obtained using all three agonists. In the case of NA or PE, EC50 values were reduced approximately fourfold, with maximum responses also increasing significantly. Endothelial cell removal caused an approximately eightfold increase in sensitivity to U46619 but no change in maximum response. The presence of oxyhaemoglobin (Hb) had a similar effect to endothelial removal on responses to NA and PE. 4. Rings obtained from 20-day pregnant rats showed significantly increased maximum responses to NA and PE when compared with those from non-pregnant animals. Removal of the endothelium or the presence of Hb caused significant shifts of the dose-response curves to the left and further increases in maxima. 5. In contrast, no differences in maximum responses to U46619 could be detected between the aortic rings of pregnant and non-pregnant animals. Removal of the endothelium from either caused increases in sensitivity which did not differ significantly.(ABSTRACT TRUNCATED AT 250 WORDS)
Jansakul
C
C
Department of Pharmacology, Monash University, Clayton, Victoria, Australia.
Boura
A L
AL
King
R G
RG
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D001685:Biological Factors / Q000494:pharmacology; D002417:Cattle; D004730:Endothelium, Vascular / Q000502:physiology*; D005260:Female; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009569:Nitric Oxide; D009638:Norepinephrine / Q000494:pharmacology; D010108:Oxyhemoglobins / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011247:Pregnancy; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D014664:Vasodilation / Q000187:drug effects
D001685:Biological Factors; D010108:Oxyhemoglobins; D011450:Prostaglandin Endoperoxides, Synthetic; D010656:Phenylephrine; D009569:Nitric Oxide; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D009638:Norepinephrine