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Voltage‐gated sodium and calcium currents in rat osteoblasts.
Author(s) -
Chesnoy-Marchais D,
Fritsch J
Publication year - 1988
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.1988.sp017043
Subject(s) - depolarization , tetrodotoxin , voltage clamp , chemistry , biophysics , egta , patch clamp , current clamp , cardiac transient outward potassium current , membrane potential , calcium , biochemistry , biology , receptor , organic chemistry
1. The whole‐cell voltage‐clamp mode of the patch‐clamp technique was used to investigate the presence of voltage‐gated inward currents in osteoblasts from newborn rat calvaria. 2. In K+‐free solutions, three kinds of inward currents could be activated by depolarization: a voltage‐gated Na+ current and two different types of Ca2+ currents. 3. The Na+ current was activated by depolarization above ‐40 mV in all the cells. It was reduced by half by 10 nM‐TTX (tetrodotoxin). 4. In an isotonic Ba2+ external solution containing TTX, and with a Cs‐EGTA internal solution buffered at pCa 8, depolarizing jumps induced both a transient Ba2+ current and a sustained Ba2+ current. The relative proportions of these two currents varied greatly among cells. 5. The transient and sustained Ba2+ currents differ with respect to their time course and their voltage dependence. 6. The depolarization‐activated inward currents were also observed under more physiological conditions, in the presence of only 2 mM‐external Ca2+ and with a K+ internal solution buffered at pCa 7. 7. A few records obtained in current clamp showed that it is possible to induce action potentials in osteoblasts.