Investigation of the cellular mechanisms of actions of digoxin and monensin by using guinea-pig papillary muscles

Abstract

This experiment was carried out to determine the possible mechanism of actions of monensin and digoxin by using guinea-pig papillary muscles. A total of 120 papillary muscles obtained from 60 guinea-pigs were used. Three treatment groups; control (%0,1 ethanol), monensin (10 μmol/l) and digoxin (3 μmol/l) were compared in normal, Na+-free, Ca2+-free, and thapsigargin-added Krebs solutions. It was found that both digoxin and monensin caused a positive inotropic effect in normal and Ca2+-free Krebs solutions. Although monensin produced a positive inotropic effect in thapsigargin-treated papillary muscles, digoxin did not show a positive inotropic effect. Because papillary muscles in Na+ -free Krebs solution showed spontaneous contractions, trusted results were not obtained in Na+ -free medium. It is concluded that monensin produces a positive inotropic effect by depending on both extracellular Ca2+ and Ca2+ released from the sarcoplasmic reticulum (SR). Digoxin, on the other hand, produces its effect by depending on the Ca2+ released from SR.

Keywords

• Monensin,digoxin,guinea pig,papillary muscle

References

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