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The effects of ATP and α,β‐methylene‐ATP on cytosolic Ca 2+ level and force in rat isolated aorta
Author(s) -
Kitajima Satoshi,
Ozaki Hiroshi,
Karaki Hideaki
Publication year - 1993
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1993.tb13803.x
Subject(s) - chemistry , verapamil , methylene , adenosine triphosphate , biophysics , extracellular , methylene blue , intracellular , agonist , adenosine , calcium , receptor , medicine , endocrinology , biochemistry , medicinal chemistry , biology , organic chemistry , photocatalysis , catalysis
1 The effects of a non‐selective P 2 ‐receptor agonist ATP and a selective P 2x ‐receptor agonist α,β‐methylene‐ATP on intracellular free Ca 2+ level ([Ca 2+ ] i ) and force were examined in rat isolated aorta without endothelium. 2 Both ATP (1–1000 μ m ) and α,β‐methylene‐ATP (0.1–100 μ m ) induced transient increase followed by small sustained increase in [Ca 2+ ] i in a concentration‐dependent manner. Compared with the force induced by a high concentration of KCl, the force induced by α,β‐methylene‐ATP was smaller and that induced by ATP was much smaller at a given [Ca 2+ ] i . 3 An L‐type Ca 2+ channel blocker, verapamil (10 μ m ), completely inhibited the high K + ‐stimulated [Ca 2+ ] i and force. Verapamil partially inhibited the transient and sustained increases in [Ca 2+ ] i induced by 10 μ m α,β‐methylene‐ATP and the sustained increase but not the transient increase induced by 1 m m ATP. 4 In the absence of extracellular Ca 2+ (with 0.5 m m EGTA) 1 m m ATP caused transient increase in [Ca 2+ ] i while 10 μ m α,β‐methylene‐ATP was ineffective 5 ATP, but not α,β‐methylene‐ATP, increased the tissue adenosine 3′:5′‐cyclic monophosphate (cyclic AMP) level. 6 These data suggest that ATP and α,β‐methylene‐ATP increase [Ca 2+ ] i by an activation of both L‐type and non‐L‐type Ca 2+ channels. In addition, ATP, but not α,β‐methylene‐ATP, increases [Ca 2+ ] i by a release of Ca 2+ from an intracellular Ca 2+ store. Possible reasons are discussed as to why the increase in [Ca 2+ ] i due to ATP and α,β‐methylene‐ATP resulted in only a small contraction.