[Modification of 2,4-dichlorophenoxyacetate-induced myotonia of cold blood muscles by variations in external Ca++ and...

The influence of several Ca++- and K+-concentrations on the mechanograms, electromyograms, membrane potentials and ion contents of myotonic cold blood muscle was investigated. In accordance with the wellknown effects of the warm blood muscle the results show that the application of Ca++ and the withdrawal of K+ improve the myotonic phenomena while the withdrawal of Ca++ and the application of K+ reinforce the myotonic reaction. The results show that 2,4-D blocks the Ca++-influx as well the transport of Na+ and K+ through the membrane. As a consequence of these results it is supposed that 2,4-D changes the charges of the muscle fiber membrane and in this way induces the myotonic phenomena. In the paper the results of the authors' investigations are being discussed in connection with the chloride-hypothesis.