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Extracellular osmotic pressure modulates sodium‐calcium exchange in isolated guinea‐pig ventricular myocytes.
Author(s) -
Wright A R,
Rees S A,
Vandenberg J I,
Twist V W,
Powell T
Publication year - 1995
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1995.sp020967
Subject(s) - extracellular , calcium , guinea pig , sodium , myocyte , osmotic pressure , chemistry , extracellular fluid , medicine , sodium calcium exchanger , endocrinology , biophysics , biology , biochemistry , organic chemistry
1. The sensitivity of the cardiac Na(+)‐Ca2+ exchange current to changes in osmotic pressure was investigated in guinea‐pig ventricular myocytes, using the whole‐cell patch‐clamp technique. 2. A hyposmotic challenge applied by removal of sucrose from the standard bathing solution reduced exchanger current, measured as the Ni(2+)‐sensitive component of whole‐cell transsarcolemmal current. These changes were fully reversible. 3. No response of whole‐cell current to hyposmosis was observed when Ca2+ was removed from the bathing solution by chelation with 1 mM EGTA. 4. Inclusion of 25 microM exchanger inhibitory peptide (XIP) in the pipette solution caused a marked reduction in the Ni(2+)‐sensitive component of membrane current, but the percentage change in Ni(2+)‐sensitive membrane slope conductance evoked by hyposmosis was the same as when XIP was omitted from the pipette solution. 5. Exposure of cells to hyperosmotic solutions produced variable responses. In a majority of cells, solutions 30% hyperosmotic compared with control evoked a persistent increase in exchanger current, whereas for solutions 50% hyperosmotic, a larger but transient increase in current was observed. 6. Over a wide range of osmolalities (50‐130% of isosmotic) the changes in Ni(2+)‐sensitive membrane slope conductance were linearly related to the changes in extracellular osmotic pressure. 7. We propose that one consequence of exposing ventricular myocytes to anisosmotic solutions is modulation of Na(+)‐Ca2+ exchange current.