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Ca 2+ ‐stores mobilization by diadenosine tetraphosphate, Ap 4 A, through a putative P 2Y purinoceptor in adrenal chromaffin cells
Author(s) -
Castro E.,
Pintor J.,
MirasPortugal M.T.
Publication year - 1992
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.1476-5381.1992.tb14421.x
Subject(s) - chromaffin cell , chemistry , adrenal medulla , endocrinology , medicine , biology , catecholamine
1 Diadenosine tetraphosphate (Ap 4 A) evoked a concentration‐dependent increase in cytosolic [Ca 2+ ] in resting chromaffin cells. The EC 50 value for this action was 28.2 ± 6.6 μ m . This effect was also produced by diadenosine pentaphosphate (Ap 5 A) with an EC 50 of 50 ± 7 μ m . 2 In contrast with this effect, pretreatment with Ap 4 A or Ap 5 A induced a 30% reduction in Ca 2+ entry following 10 μ m dimethylphenylpiperazinium. 3 The elevation in cytosolic [Ca 2+ ] induced by AP 4 A was persistent in ≅ 100 n m external [Ca 2+ ] and was sensitive to depletion of internal Ca 2+ stores by a bradykinin prepulse or whole cell depletion in Ca 2+ . 4 The effect of Ap 4 A was mimicked and desensitized by the agonist adenosine 5′‐O‐(2‐thiodiphosphate), and blocked by the P 2Y ‐receptor antagonist, cibachrome blue. The P 2X ‐receptor agonist α,β‐methylene adenosine 5′‐triphosphate was inactive both by itself or in combination with Ap 4 A. This is compatible with a P 2Y ‐purinoceptor‐mediated action.