Abstract.
Intracellular dialysis with the solution containing the G protein activator, AlF complex, induced an inward nonselective cation current (I NS) at −55 mV in chromaffin cells. Amplitudes of I NS induced by dialysis with ATP-free AlF solutions progressively diminished as cells were pretreated with cyanide, a mitochondrial inhibitor. After a 10-min pretreatment, generation of I NS by the AlF complex depended on exogenous ATP delivered from pipette solution. The relationship between amplitudes of I NS and concentrations of MgATP was well expressed by a rectangular hyperbola with an EC50 of 0.265 mm. This result suggests that the cyanide treatment almost depleted ATP near the plasma membrane. On the other hand, a similar cyanide treatment of adrenal medullary preparations did not induce a marked decrease in cellular ATP content. GTP, ITP, or UTP could not substitute for ATP in generation of I NS by the AlF complex. Similarly, the substitution of ATP with non- or poorly hydrolyzable ATP analogues did not aid in generating I NS. Bath application of the kinase inhibitor, H-7 (100 μm), suppressed AlF-induced I NS in a manner depending on intracellular Mg2+. We conclude that ATP is a prerequisite for generation of I NS as a phosphoryl donor and that mitochondria is the main source of ATP.
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Received: 17 April 1996/Revised: 26 July 1996
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Inoue, M., Ogawa, K., Fujishiro, N. et al. Role and Source of ATP for Activation of Nonselective Cation Channels by AlF Complex in Guinea Pig Chromaffin Cells. J. Membrane Biol. 154, 183–195 (1996). https://doi.org/10.1007/s002329900143
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DOI: https://doi.org/10.1007/s002329900143