Mediation of endothelium-dependent relaxation: different response patterns in rat and rabbit basilar artery.
The endothelial lining of blood vessels plays an important role in the control of arterial tone by releasing a number of vasoactive factors. Among these, nitric oxide (NO) or a NO containing moiety, some cyclooxygenase products such as prostacyclin (PGl2) and a still hypothetical hyperpolarizing factor may induce dilatation/relaxation. In the present study, the functional importance of these factors in mediating endothelium-dependent relaxation has been investigated in isolated cerebral arteries. Acetylcholine (ACh) was used to induce endothelium-dependent relaxation of ring segments obtained from rat and rabbit basilar artery (BA). Glibenclamide (10(-6) M) which acts as an inhibitor of ATP-sensitive K+ channel activation did not affect the relaxant action of ACh. With the cyclooxygenase blocked by indomethacin (10(-6) M) ACh-induced relaxation was unaffected in rat BA and only slightly attenuated in rabbit BA. The NO synthase inhibitor NG-nitro-L-arginine (L-NNA, 10(-6) and 10(-5) M) completely abolished ACh-induced relaxation in rat BA and resulted in a moderate inhibition in rabbit BA (10(-5) and 10(-4) M). However, ACh-induced relaxation of rabbit BA was abolished in the presence of both indomethacin and L-NNA. These results indicate that endothelium-dependent relaxation of large cerebral arteries is mediated by NO acting alone or in concert with a relaxant cyclooxygenase product. In addition, there is no indication for the action of an endothelium-derived hyperpolarizing factor different from NO or a prostanoid.
Mackert
J L
JL
Department of Physiology, University of Munich, Germany.
Parsons
A A
AA
Wahl
M
M
Schilling
L
L
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001488:Basilar Artery / Q000187:drug effects / Q000502:physiology*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005905:Glyburide / Q000494:pharmacology; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D019335:Nitroarginine / Q000494:pharmacology; D011817:Rabbits / Q000502:physiology*; D051381:Rats / Q000502:physiology*; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
D016861:Cyclooxygenase Inhibitors; D004791:Enzyme Inhibitors; D019335:Nitroarginine; D019001:Nitric Oxide Synthase; D000109:Acetylcholine; D005905:Glyburide; D007213:Indomethacin