P2-purinoceptor-mediated membrane currents in DDT1 MF-2 smooth muscle cells.
The electrophysiological response evoked by ATP was investigated in the DDT1 MF-2 smooth muscle cell line using the microelectrode technique and the whole-cell patch clamp technique. Application of ATP (10(-3) M) to the bathing solution caused a small initial depolarization of the cell membrane, followed by hyperpolarization and slow depolarization. During voltage clamping (-50 mV) a triphasic response was recorded on stimulation with ATP (10(-4)-10(-3) M). A short-lasting inward current was followed by a transient outward current and a slowly decreasing inward current. This response was not affected by the receptor antagonists, propranolol (3 X 10(-6) M), phentolamine (3 X 10(-6) M), atropine (3 X 10(-6) M) or theophylline (10(-3) M). The ATP-induced currents were not modified by the voltage-dependent channel blocking agents, tetraethyl ammonium (3 X 10(-3) M), 3,4-diaminopyridine (10(-3) M), tetrodotoxin (3 X 10(-7) M) or diltiazem (10(-5) M). The fast inward current was not detectable at a low ATP concentration (10(-5) M). The outward current showed a reversal potential near -76 mV, which equals the potassium equilibrium potential. This current was abolished after neutralization of the potassium electrochemical gradient. The outward current was suppressed under calcium-free conditions and also in the presence of tolbutamide (10(-4) M) or glipizide (5 X 10(-6) M). Guanosine triphosphate (5 X 10(-6) M) promoted the outward current, while this current was inhibited in the presence of guanosine diphosphate (5 X 10(-6) M).(ABSTRACT TRUNCATED AT 250 WORDS)
Molleman
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University of Groningen, Department of Pharmacology and Clinical Pharmacology, The Netherlands.
Nelemans
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Den Hertog
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D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001030:Apamin / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004563:Electrochemistry; D004594:Electrophysiology; D007473:Ion Channels / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects; D008839:Microelectrodes; D009130:Muscle, Smooth / Q000166:cytology / Q000378:metabolism*; D011983:Receptors, Purinergic / Q000187:drug effects*
D007473:Ion Channels; D011983:Receptors, Purinergic; D001030:Apamin; D000255:Adenosine Triphosphate