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MECHANISM OF MECHANICAL INHIBITION OF SMOOTH MUSCLE BY OUABAIN
Author(s) -
BOSE D.
Publication year - 1975
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1975.tb07618.x
Subject(s) - ouabain , sodium , extracellular , potassium , chemistry , taenia coli , inhibitory postsynaptic potential , intracellular , medicine , endocrinology , biophysics , guinea pig , pharmacology , biochemistry , biology , organic chemistry
1 Ouabain (10 μg/ml) caused an initial increase followed by a decrease in tension in guinea‐pig taenia coli bathed in normal sodium and potassium containing medium. 2 The excitatory effect of ouabain was prevented by the elevation of extracellular potassium while the inhibitory effect was abolished in the absence of sodium in the bathing medium. 3 In the presence of sodium, the inhibitory effect of ouabain disappeared when the drug was washed out, but in the presence of lithium (which is not extruded by the Na‐K pump) the inhibition was not abolished. 4 The inhibitory effect of ouabain was accompanied by an increase in tissue Na and a decrease in tissue K concentration. The increase in intracellular [ 45 Ca] which occurred when extracellular [K] was varied, was also reduced by ouabain. 5 It is concluded that a high intracellular level of sodium inhibits contractions in visceral smooth muscle probably by a mechanism involving decreased Ca influx.