Selective Inhibition of Potassium Contracture in Guinea Pig Taenia Coli by Ruthenium Red

Abstract

Effects of ruthenium red on isotonic KCl induced contracture (K-contracture), cellular 45Ca uptake and 45Ca binding to surface membranes were examined in the smooth muscle cells of guinea pig taenia coli. These results were compared with those using lanthanum (La3+). The tonic component of the K-contracture was selectively inhibited by 1 mM ruthenium red. In contrast, 1 mivt La3+ inhibited the phasic component of the K-contracture to a large extent. Use of 1 mM ruthenium red selectively inhibited the tonic component of K-contracture and caused a marked decrease in cellular 45Ca uptake in that component of K-contracture. In contrast, 1 mM La3+ largely inhibited the phasic component and caused a significant decrease in cellular 45Ca in that component. According to Scatchard plot analysis, there are two kinds of Ca2+ binding sites of high and low affinity, respectively, on the surface membrane of the taenia coli. One mM ruthenium red suppressed those of low affinity more strongly than those of high affinity. In contrast, 1 mM La3+ suppressed high affinity sites more markedly than low affinity sites. Based on these results, it seems possible to conclude that ruthenium red mainly blocks the initial binding sites linked with Ca2+ influx which is related to the production of the tonic component while La3+ blocks those sites related to the phasic component of the K-contracture of guinea pig taenia coli.

Effects of ruthenium red on membrane ionic currents in urinary bladder smooth muscle cells of the guinea-pig

“…Morphological analysis using electron microscopy also indicates that RuR enters skeletal and cardiac myocytes [5]. On the other hand, the cytosol of smooth muscle cells does not appear to be stained by RuR [18]. In the present study, external 10 µM RuR decreased BK channel activity only by 20% in outside-out patches but it decreased STOCs and I caf by 50%.…”

“…The activation of Ca 2+ -dependent K + current (I K-Ca ) may be mediated by CICR which is triggered by Ca 2+ influx through voltage-dependent Ca 2+ channels [18,28,35]. It is expected, therefore, that RuR reduces I K-Ca indirectly via the block of the RyR [39], but details have not been clarified.…”

Contribution of intracellular stored calcium to contractile activation in contractures of stomach circular muscle of Bufo vulgaris formosus.

“…This assumption may be supported by the present results that K-induced contracture was inhibited markedly by procaine, as in the case of ACh-induced contracture which was thought to be highly dependent on intracellular stored Ca. Thus, the trigger Ca for Ca release from the intracellular stores can be considered to enter via some Ca binding sites which are sensitive to La (KAWAMURA and YABU, 1978) and much more resistant to verapamil, because K-induced contracture was little inhibited by 10 ,uM verapamil ( Fig. 3B) which is also known as a Ca blocker (GOLENHOFEN and LAMMEL, 1972).…”

Influence of calixarene C-99 on contractile activity of rat large intestine smooth muscles

“…Зо-крема, на препаратах гладеньких м'язів taenia coli з'ясовано [14], що аплікування рутенієвого червоного супроводжується потужним зниженням саме тонічної складо-вої гіперкалієвої контрактури, тоді як фазне скорочення у цьому разі інгібується зна-чно меншою мірою. Відомо, що рутенієвий червоний неспецифічно пригнічує функ-цію Са 2+ -транспортувальних систем: блокує TRPA1-канали плазматичної мемб рани (в нашому випадку не є актуальним, оскільки ці канали активуються при температу-рах нижче 17 °С), блокує роботу Са…”