Abstract
The effect of change of the external ionic composition on "Na-loaded" and "K-depleted" soleus muscle fibres of K-deficient rats was investigated by recording resting membrane potentials. The addition of K, Rb, Cs and NH4 ions to K-free Krebs solution bathing "Na-rich" muscles resulted in a rapid hyperpolarization. The hyperpolarization was abolished by removing the above cations, cooling to ca. 4 degrees C, and adding 0.1 mM ouabain. The effectiveness of cations for activating the electrogenic Na pump was Rb greater than or equal to K greater than NH4 greater than Cs, and NH4 ions seemed to be unique in their stimulating action. The resting cell membrane of "Na-rich" muscles is permeable to cations in the order of Rb = K greater than Cs greater than NH4. Reducing Na ions in Krebs solution had no effect on the rate of Na-pumping in "Na-rich" muscle fibres at a given K concentration. It is concluded that the external K ions could be replaced by Rb, Cs and NH4 ions in activating the electrogenic Na pump in "Na-rich" soleus muscle fibres, but that the electrogenic Na pump in this tissue does not require the external Na ions.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
