Abstract
Intracellular Ca, Na and H selective microelectrodes were used to study the effects of reduction of the extracellular Na concentration, [Na]0, on the free intracellular Ca concentration, [Ca]i, Na activity, (aNa i), and intracellular pH (pHi) in sheep heart Purkinje fibres. 1. Reduction of [Na]0 from 140 mM to 14 mM produced a decrease of aNa i, and increase of free [Ca]i, and normally an increase of resting tension. 2. Inhibition of the Na-K pump by 10-5 M acetylstrophanthidin produced a slow rise of [Ca]i and resting tension. 3. The magnitude of the increase of free [Ca]i (and tension) produced by [Na]0 reduction was greatly enhanced when the Na-K pump is inhibited by either acetylstrophanthidin or K-free solutions. 4. We suggest that this enhanced rise of free [Ca]i in the presence of Na-K pump inhibition is due to Ca loading of intracellular Ca buffering systems during the pump inhibition. 5. Addition of NH4Cl produced a transient decrease of free [Ca]i that accompanied an alkaline change in pHi. Removal of NH4Cl (which produced a transient intracellular acidification) produced a transient increase of free [Ca]i. We conclude that a close relationship exists between the control of free [Ca]i and pHi which may be due to competition at, or common use of, intracellular buffering systems.
Original language | English (US) |
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Pages (from-to) | 171-178 |
Number of pages | 8 |
Journal | Pflügers Archiv European Journal of Physiology |
Volume | 393 |
Issue number | 2 |
DOIs | |
State | Published - Apr 1982 |
Externally published | Yes |
Keywords
- Calcium
- Cardiac glycoside
- Heart
- pH
- Purkinje fibres
- Sodium
ASJC Scopus subject areas
- Physiology