Effects of nifedipine ryanodine and cyclopiazonic acid on tension development of ileal longitudinal muscle by manganese ions in Ca(2+)-free high-K+ medium.
作者信息
Nasu T, Arakaki H, Shibata H
机构信息
Department of Veterinary Pharmacology, Faculty of Agriculture, Yamaguchi University, Japan.
出版信息
Gen Pharmacol. 1995 Oct;26(6):1255-60. doi: 10.1016/0306-3623(95)00017-u.
Mn2+ (5 mM) could evoke the contraction in a Ca(2+)-free, high-K+ (60 mM) medium in ileal longitudinal muscle. Nifedipine, L-type Ca2+ channel blocker, inhibited dose-dependently both the contraction and manganese uptake in the presence of 5 mM Mn2+, in the Ca(2+)-free, high-K+ medium. 2. However, both ryanodine, Ca2+ release blocker from SR and cyclopiazonic acid, specific SR Ca(2+)-ATPase blocker, had no effects on the contractions evoked by Mn2+ and the manganese uptake in the Ca(2+)-free, high-K+ medium. 3. These results suggest that Mn2+ did not liberate Ca2+ at the storage sites during the Mn(2+)-induced contraction in Ca(2+)-free, high-K+ medium. Mn2+ is entering via voltage-dependent Ca2+ channels in the ileal cell membranes and it directly activates the contractile elements.
