title: The influence of nitric oxide on tumour vascular tone.
abstract: Acetylcholine and sodium nitroprusside, which vasodilate via release of NO by endothelium-dependent and endothelium-independent mechanisms respectively, had little effect on tumour vascular resistance when administered to tissue-isolated tumours perfused in their normal state. However, under phenylephrine-induced vasoconstriction, sodium nitroprusside induced vasodilation whilst acetylcholine induced a small vasoconstriction. Phenylephrine itself induced an oscillatory change in tumour perfusion pressure. The nitric oxide synthase (NOS) inhibitor N omega-nitro-L-arginine (L-NNA) caused a dose-dependent increase in vascular resistance in ex vivo perfused tumours which was greater than that in normal perfused hindlimbs. Systemic administration of L-NNA caused a 50% decrease in tumour blood flow which was a larger effect than in any of the normal tissues studied except spleen and skeletal muscle. Modification of NOS activity in tumours is a promising means for selective tumour blood flow modification. Investigation of endothelium-dependent versus endothelium-independent methods for modifying tumour blood flow may provide methods for further selectivity.
authors.affiliation: Tumour Microcirculation Group, CRC Gray Laboratory, Mount Vernon Hospital, Northwood, Middlesex, England.
authors.forename: G M
authors.initials: GM
authors.lastname: Tozer
authors.forename: V E
authors.initials: VE
authors.lastname: Prise
authors.forename: K M
authors.initials: KM
authors.lastname: Bell
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002296:Carcinosarcoma / Q000098:blood supply*; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000503:physiopathology*; D008297:Male; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase; D019335:Nitroarginine; D009599:Nitroprusside / Q000494:pharmacology*; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012039:Regional Blood Flow / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects*; D014661:Vasoconstriction / Q000187:drug effects*; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D009599:Nitroprusside; D010656:Phenylephrine; D019335:Nitroarginine; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D000109:Acetylcholine