Role of calcium in different layers of vascular smooth muscle in norepinephrine contraction.
The role of calcium present in adventitial and media-intimal layers of rabbit aorta in the fast (F-) and the slow (S-) components of norepinephrine (10(-5) M) contraction was evaluated in this study. An increased sensitivity and decreased maximum tension to response to norepinephrine was observed in adventitia-free aorta as compared to whole aorta. Incubation in calcium-free Ringer solution with or without EDTA decreased the F-component of norepinephrine contraction of the adventitia-free aorta, whereas the F-component of the whole aorta was not affected. The S-component of both preparations was abolished in calcium-free Ringer solution. Norepinephrine increased calcium uptake into whole and adventitia-free aortic strips. An increase in calcium uptake induced by norepinephrine during the F-component of norepinephrine contraction was also observed. 45Ca efflux studies revealed the presence of an exchangeable calcium fraction in the adventitial layer. These data suggest that F-component of norepinephrine contraction is partially dependent on the extracellular calcium distributed in the adventitial layer of rabbit aorta.
D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D001158:Arteries / Q000502:physiology*; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D004492:Edetic Acid / Q000494:pharmacology; D005260:Female; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D011817:Rabbits; D012964:Sodium / Q000378:metabolism
D010042:Ouabain; D004492:Edetic Acid; D012964:Sodium; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine