ISSN:
1474-8673
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Chemistry and Pharmacology
,
Medicine
Notes:
1 Cupric ions (Cu2+), at concentrations above 0.03 mm, induced a progressive increase in the tonic contraction of guinea-pig ileal longitudinal muscle. Maximal contraction of 0.1 mm Cu2+ attained a level above that of the 60-mm K+-induced tonic response, within 20 min of application. The tension induced by Cu2+ persisted for more than several hours. Tetrodotoxin (3 × 10−6 m) had no effect on the contraction induced by 0.1 mm Cu2+. 2 After incubation in a Ca2+-free medium, the ileal response to 0.1 mm Cu2+ was lost. Nifedipine, a L-type Ca2+ channel blocker, dose-dependently inhibited contractions induced by Cu2+. 3 As the duration of the first application of 0.1 mm Cu2+ increased above 30 min, after washing with normal medium, the contractile response to a second application of 0.1 mm Cu2+ decreased gradually. After 150 min of the first application of 0.1 mm Cu2+, a second application of Cu2+ could not evoke any contraction. 4 After the application of 0.1 mm Cu2+ for 150 min, when muscles were washed with a medium containing 1 mm EDTA, the response to 0.1 mm Cu2+ returned to a greater extent in the normal Ca2+ medium. 5 In conclusion, Cu2+ (0.1 mm) induced a maximal ileal tension above that of the K-induced tonic response within 20 min. The ileal contraction to Cu2+ persisted for more than several hours and depended on extracellular Ca2+ concentrations. It is possible that a part of Cu2+, bound to a EDTA-inaccessible site, also has a tension inhibitory effect.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1474-8673.2004.00320.x
