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Properties of ionic currents induced by external ATP in a mouse mesodermal stem cell line.
Author(s) -
Kubo Y
Publication year - 1991
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.1991.sp018815
Subject(s) - biophysics , adenosine triphosphate , intracellular , chemistry , patch clamp , caffeine , adenosine , biochemistry , biology , endocrinology , receptor
1. ATP was puff applied to cells of a mesodermal stem cell line, C3H10T1/2, and the responses were studied by whole‐cell patch clamp recording. 2. In 91% of the cells (90/99), K+ current lasting for tens of seconds was observed after several seconds latency. The current showed outward rectification. In 10% of the cells (9/99), ATP induced Cl‐ current which also lasted for tens of seconds after several seconds latency, but showed little rectification. In 6% of these cells (5/99), both K+ and Cl‐ currents were induced by ATP. 3. The K+ current induced by ATP was dose dependent, with a Kd of 0.4 microM. The effects of ATP analogues were tested at a concentration of 20 microM. ADP and ATP‐gamma‐S induced the K+ current, while AMP and adenosine did not. alpha, beta‐Methylene ATP produced a diminished K+ current. 4. The ATP‐induced K+ current was not observed when EGTA in the internal solution was raised from 0.1 to 5 mM. In Fluo‐3‐loaded cells, an increase in intracellular Ca2+ concentration induced by the application of ATP was observed, and the time course was similar to the induced K+ current. Both the increase in intracellular Ca2+ and the K+ current were induced by ATP even in Ca(2+)‐free external solution. Ryanodine (50 microM) in the external solution did not affect the ATP response, and application of 10 mM‐caffeine alone to the external solution did not induce any response. 5. The variance of the steady‐state fluctuations in the course of the ATP‐induced slow K+ current was analysed. The single‐channel conductance was estimated as 2.7 pS at 0 mV with external and internal K+ concentrations of 5 and 140 mM respectively. The K+ current was not affected by apamin at concentrations of up to 1 microM but was reduced to one‐third by 140 mM‐tetraethylammonium (TEA). 6. It was concluded that puff‐applied ATP has two main effects in the mesodermal stem cells: an increase in the intracellular Ca2+ concentration and a succeeding hyperpolarization due to the Ca(2+)‐activated K+ conductance which is present in this cell. The significance of the increase in intracellular Ca2+ caused by ATP is discussed.