Ca2+‐stores mobilization by diadenosine tetraphosphate, Ap4A, through a putative P2Y purinoceptor in adrenal chromaffin cells
Open Access
- 1 August 1992
- journal article
- Published by Wiley in British Journal of Pharmacology
- Vol. 106 (4), 833-837
- https://doi.org/10.1111/j.1476-5381.1992.tb14421.x
Abstract
1 Diadenosine tetraphosphate (Ap4A) evoked a concentration-dependent increase in cytosolic [Ca2+] in resting chromaffin cells. The EC50 value for this action was 28.2 ± 6.6 μm. This effect was also produced by diadenosine pentaphosphate (Ap5A) with an EC50 of 50 ± 7 μm. 2 In contrast with this effect, pretreatment with Ap4A or Ap5A induced a 30% reduction in Ca2+ entry following 10 μm dimethylphenylpiperazinium. 3 The elevation in cytosolic [Ca2+] induced by AP4A was persistent in ≅ 100 nm external [Ca2+] and was sensitive to depletion of internal Ca2+ stores by a bradykinin prepulse or whole cell depletion in Ca2+. 4 The effect of Ap4A was mimicked and desensitized by the agonist adenosine 5′-O-(2-thiodiphosphate), and blocked by the P2Y-receptor antagonist, cibachrome blue. The P2X-receptor agonist α,β-methylene adenosine 5′-triphosphate was inactive both by itself or in combination with Ap4A. This is compatible with a P2Y-purinoceptor-mediated action.Keywords
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