Endothelium-dependent and -independent relaxation by dopamine in the rabbit pulmonary artery.
1. The relaxing response of dopamine (DA) was studied in the rabbit pulmonary artery. DA caused concentration-related relaxation in helically cut strips of the artery contracted with prostaglandin F2 alpha in the presence of prazosin. 2. The DA-induced relaxation in endothelium-denuded strips was reduced to about 40% compared with that in endothelium-intact strips. 3. Methylene blue and haemoglobin, inhibitors of endothelium-dependent relaxation, reduced the DA-induced relaxations in endothelium-intact strips to the level of endothelium-denuded strips. These results indicate that the DA-induced relaxation is partially mediated or modified by the release of endothelium-derived relaxing factor (EDRF). 4. Apomorphine, as a DA agonist, caused concentration-dependent relaxation in endothelium-intact strips. Bromocriptine, a DA2 agonist, produced only a little relaxation at higher concentration. 5. In endothelium-intact strips, haloperidol, a DA antagonist, and the DA1 antagonists, fluphenazine and SCH 23390 inhibited DA-induced relaxations. On the other hand spiperone and domperidone, DA2 antagonists, were inactive. 6. In endothelium-denuded strips, fluphenazine and SCH 23390 inhibited DA-induced relaxations, but domperidone was inactive. 7. These results indicate that the DA-induced relaxation is mediated by DA receptors, and that DA1 receptors are involved in both endothelium-dependent and -independent relaxation in the rabbit pulmonary artery.
Yamauchi
M
M
Department of Pharmacology, Shimane Medical University, Japan.
Kobayashi
Y
Y
Shimoura
K
K
Hattori
K
K
Nakase
A
A
D000818:Animals; D004298:Dopamine / Q000494:pharmacology*; D018492:Dopamine Antagonists; D004730:Endothelium, Vascular / Q000502:physiology*; D005260:Female; D006454:Hemoglobins / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008751:Methylene Blue / Q000494:pharmacology; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D011651:Pulmonary Artery / Q000187:drug effects; D011817:Rabbits; D011954:Receptors, Dopamine / Q000187:drug effects; D013482:Superoxide Dismutase / Q000494:pharmacology
D018492:Dopamine Antagonists; D006454:Hemoglobins; D011954:Receptors, Dopamine; D013482:Superoxide Dismutase; D008751:Methylene Blue; D004298:Dopamine