Origin of Ca2+ necessary for carbachol-induced contraction in longitudinal muscle of the proximal colon of rats.
The origin of Ca2+ necessary for carbachol (CCh)-induced contraction of longitudinal muscle of the proximal colon of rats was studied. CCh induced contraction of the muscle consisting of two phases, phasic and tonic phases, with a concomitant biphasic increase in [Ca2+]i. After removal of Ca2+ from the bathing solution of the colonic segments, CCh-induced contraction was rapidly inhibited; there was almost complete inhibition 1 min after the removal. Nicardipine, a blocker of voltage-dependent calcium channel, also significantly inhibited CCh-induced contraction. On the other hand, treatment of the colonic segments with thapsigargin, an inhibitor of sarcoplasmic reticulum (SR) Ca2+-ATPase, did not significantly affect the contraction except causing a slight decrease in the rate of contraction. These results suggest that Ca> entering through voltage-dependent calcium channels, but not released from SR, is essential for CCh-induced contraction of longitudinal muscle of the proximal colon of rats. This strict dependency of the CCh-induced contraction on extracellular Ca2+ was discussed in relation to the results obtained in the fundus of rats.
Takeuchi
T
T
Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, Osaka Prefecture University, Sakai, Japan. takeuchi@vet.osakafu-u.ac.jp
Sumiyoshi
M
M
Kitayama
M
M
Hirayama
N
N
Fujita
A
A
Hata
F
F
D062365:Aminobenzoates / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology*; D002723:Chlorobenzoates; D002934:Cinnamates / Q000494:pharmacology; D003106:Colon / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005769:Gastrointestinal Motility / Q000187:drug effects; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009529:Nicardipine / Q000494:pharmacology; D010277:Parasympathomimetics / Q000494:pharmacology*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology; D062367:ortho-Aminobenzoates
D062365:Aminobenzoates; D002121:Calcium Channel Blockers; D002723:Chlorobenzoates; D002934:Cinnamates; D004791:Enzyme Inhibitors; D010277:Parasympathomimetics; D010726:Phosphodiesterase Inhibitors; D062367:ortho-Aminobenzoates; D002110:Caffeine; D019284:Thapsigargin; D002217:Carbachol; C060048:2-(4-amylcinnamoyl)amino-4-chlorobenzoic acid; D009529:Nicardipine; D002118:Calcium