AJP - Cell Physiology, Vol 255, Issue 4 C433-C441, Copyright © 1988 by American Physiological Society
Effect of leukotriene C4 on electromechanical activity and Ca2+ uptake in taenia coli
A. Zschauer, E. K. Matthews and B. P. Richardson
Department of Pharmacology, University of Cambridge, United Kingdom.
The actions of leukotriene C4 (LTC4) on electromechanical activity and
45Ca2+ uptake in guinea pig taenia coli were investigated. The contractile
action of LTC4 was abolished by the removal of extracellular Ca2+. LTC4
concentrations eliciting a maximal contraction in normal medium produced no
response in preparations depolarized with KCl. In single sucrose gap
studies, LTC4 increased both the frequency of electrical spiking and
tension. These effects were blocked by the dihydropyridine Ca2+-channel
antagonist PY 108-068 and by the leukotriene receptor antagonist FPL 55712.
In double sucrose gap experiments, LTC4 caused a small depolarization
without measurable change in membrane conductivity; increased spontaneous
electrical activity was again accompanied by an increase in tension. LTC4
caused a detectable increase in 45Ca2+ uptake only at extracellular Ca2+
concentrations less than 1 mM, and this was again inhibited by PY 108-068
or FPL 55712. It is concluded that the contractile effects of LTC4 in
guinea pig taenia coli occur as a consequence of its ability to open
voltage-sensitive Ca2+ channels, an effect that may occur independently of
membrane depolarization.
