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  • Title: Mechanism of inhibition of smooth muscle of guinea-pig taenia coli by chloramphenicol.
    Author: Pramanik P, Datta SC, Mitra C.
    Journal: J Physiol Pharmacol; 1994 Mar; 45(1):133-45. PubMed ID: 8043903.
    Abstract:
    The effects of antibiotic chloramphenicol (CAP) on Ca(2+)-ATPase activity and muscle tension were examined in guinea-pig taenia coli. In general, when CAP was added to the resting tissue no inhibition was observed except when a tonus was present, caused by either ouabain, high K+ or acetylcholine. Ouabain and high K(+)-induced sustained contractions were concentration-dependently inhibited by CAP. The sustained contraction induced by high K+ was more strongly inhibited by CAP than ouabain (IC50 value: high K+ 0.29 mumol/ml; ouabain 0.34 mumol/ml). In Ca(2+)-free solution, inhibition of ouabain-induced sustained contracture by CAP was more pronounced. CAP increased the activity of Ca(2+)-ATPase in taenia coli in all experiments. In presence of cystine, CAP-induced inhibition and increase in Ca(2+)-ATPase activity could not be observed. CAP analogue thiamphenicol (TAP), devoid of p-NO2 group, showed insignificant response on smooth muscle inhibition and Ca(2+)-ATPase activity. These findings suggest that CAP inhibits smooth muscle contractility by decreasing cytosolic Ca2+ ([Ca2+]i) level through a cGMP mediated increase in Ca(2+)-ATPase activity and this action is possibly related with the p-NO2 group present in its molecule like other nitro-compounds.
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