The effect of lowered extracellular Na+ concentration on ultraviolet light-induced relaxation of vasoconstricted rabbit isolated thoracic aorta.
The effect of lowering extracellular ion concentration on ultraviolet (UV) light-induced photorelaxation of norepinephrine(NE)-constricted rabbit isolated thoracic aorta was investigated. The magnitude of the photorelaxation response (similar to acetylcholine-induced, but not nitroprusside-induced, relaxation) progressively declined, in the absence of an effect on NE-induced vasoconstriction, as the total extracellular ion concentration was progressively reduced. This diminution in the photorelaxation response was duplicated by isosmotic lowering of the extracellular concentration of Na+, but not other ions, from 145 to 25 mM and was not restored by the replenishment of the Na+ deficiency by equimolar amounts of mannitol or Li+. In contrast, choline fully substituted for Na+. These findings suggest a fundamental difference in the ion dependency (and, hence, the mechanisms) of UV-induced photorelaxation and the vasorelaxations induced by acetylcholine or sodium nitroprusside.
Raffa
R B
RB
R.W. Johnson Pharmaceutical Research Institute, Spring House, PA 19477-0776.
Aceto
J F
JF
Goldschmidt
J E
JE
Tallarida
R J
RJ
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000378:metabolism / Q000528:radiation effects; D002118:Calcium / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D005260:Female; D008094:Lithium / Q000378:metabolism; D009126:Muscle Relaxation / Q000528:radiation effects*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000502:physiology / Q000528:radiation effects*; D009638:Norepinephrine / Q000494:pharmacology; D011817:Rabbits; D012964:Sodium / Q000378:metabolism*; D014466:Ultraviolet Rays; D014661:Vasoconstriction / Q000187:drug effects
D002712:Chlorides; D008094:Lithium; D012964:Sodium; D000109:Acetylcholine; D002118:Calcium; D009638:Norepinephrine