An ATP‐activated conductance in pheochromocytoma cells and its suppression by extracellular calcium.

K. Nakazawa, K. Fujimori, A. Takanaka, Kazuhide Inoue

Research output: Contribution to journalArticle

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Abstract

1. ATP‐activated inward current in PC12 pheochromocytoma cells was characterized using the whole‐cell voltage‐clamp technique. 2. ATP (100 microM) applied extracellular elicited an inward rectifying current with a reversal potential of about +7 mV. The current was desensitized in seconds in spite of continued presence of ATP. 3. A comparison was made of the ability of ATP and its analogues. The order of potency in activating the inward current was ATP greater than ATP gamma S greater than ADP; AMP, adenosine and alpha, beta‐methylene ATP were inactive at concentrations up to mM. 4. The ATP‐activated current was also observed when external Na+ and Ca2+ were replaced with K+, TEA, Tris or glucosamine. The order of ion selectivity was Na+ greater than K+ greater than TEA not equal to Tris greater than glucosamine. 5. The ATP‐activated current was also recorded in extracellular solutions containing Ca2+ as the only external cation. The amplitude increased as the concentration of Ca2+ was increased in the range between 1.8 and 16.2 mM. However, the current amplitude decreased at higher Ca2+ concentrations and the current was not recorded in 110 mM‐Ca2+ solution. 6. In the presence of 140 mM‐Na+ in the external solution, the current amplitude also decreased as the external Ca2+ concentration was increased (from 1.8 to 16.2 mM). 7. The results indicate that Ca2+ as well as monovalent cations permeate through the ATP‐sensitive pathway and that Ca2+ blocks ion permeation, including its own permeation through the pathway. This regulation by extracellular Ca2+ is different to the ATP‐activated current in smooth muscle cells.

Original languageEnglish
Pages (from-to)257-272
Number of pages16
JournalThe Journal of Physiology
Volume428
Issue number1
DOIs
Publication statusPublished - Sep 1 1990
Externally publishedYes

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Pheochromocytoma
Adenosine Triphosphate
Calcium
Glucosamine
Ions
Monovalent Cations
PC12 Cells
Adenosine Monophosphate
Adenosine
Adenosine Diphosphate
Smooth Muscle Myocytes
Cations

All Science Journal Classification (ASJC) codes

  • Physiology

Cite this

An ATP‐activated conductance in pheochromocytoma cells and its suppression by extracellular calcium. / Nakazawa, K.; Fujimori, K.; Takanaka, A.; Inoue, Kazuhide.

In: The Journal of Physiology, Vol. 428, No. 1, 01.09.1990, p. 257-272.

Research output: Contribution to journalArticle

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