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| 5: Vascul Pharmacol. 2003 Jan;40(1):29-33. |
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- The effects of nifedipine and thapsigargin on the
responses of pressurized rat mesenteric artery to 5-hydroxytryptamine and
norepinephrine.
Sofola OA, Adegunloye BJ, Knill A.
Institute for Cardiovascular Studies, University of Leeds, LS2 9JT, Leeds, UK
The responses of isolated pressurized second order mesenteric resistance
arteries of Wistar rats, superfused with physiological salt solution (PSS)
were determined to 5-hydroxytryptamine (5-HT) and norepinephrine (NE). The
contractility of the vessel was enhanced in response to 5-HT compared to NE
(P<.001, ANOVA). The L-type calcium ion channel blocker, nifedipine (10(-6) M)
abolished the response to either 5-HT or NE. In vessels with intact
endothelium, thapsigargin (TG, 10(-6) M), which inhibits uptake of calcium
ions into intracellular stores, significantly reduced the contractile response
to 5-HT (P<.02) but had little or no effect on the response to NE (P=.2).
However, in vessels denuded of the endothelium, there was no significant
difference in the response of the mesenteric artery, after TG, to either 5-HT
or NE. The results indicate that, in the rat mesenteric resistance vessel,
both 5-HT and NE use calcium ions from extracellular sources for contraction,
while NE relies mainly on extracellular ion influx with little or no
contribution from intracellular sources. The reduced response of the de-endothelized
vessel to 5-HT after TG suggests that the utilization of intracellular stores
by this agonist is endothelium-dependent. These observations may explain the
enhanced responsiveness of the mesenteric artery to 5-HT when compared with
NE.
PMID: 12646407 [PubMed - in process]
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