title: Ca(2+)-stores mobilization by diadenosine tetraphosphate, Ap4A, through a putative P2Y purinoceptor in adrenal chromaffin cells.
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 microM. This effect was also produced by diadenosine pentaphosphate (Ap5A) with an EC50 of 50 +/- 7 microM. 2. In contrast with this effect, pretreatment with Ap4A or Ap5A induced a 30% reduction in Ca2+ entry following 10 microM dimethylphenylpiperazinium. 3. The elevation in cytosolic [Ca2+] induced by Ap4A was persistent in approximately 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 alpha,beta-methylene adenosine 5'-triphosphate was inactive both by itself or in combination with Ap4A. This is compatible with a P2Y-purinoceptor-mediated action.
authors.affiliation: Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense de Madrid, España.
authors.forename: E
authors.initials: E
authors.lastname: Castro
authors.forename: J
authors.initials: J
authors.lastname: Pintor
authors.forename: M T
authors.initials: MT
authors.lastname: Miras-Portugal
mesh_terms: D000311:Adrenal Glands / Q000502:physiology*; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002837:Chromaffin Granules / Q000502:physiology*; D015226:Dinucleoside Phosphates / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D011983:Receptors, Purinergic / Q000187:drug effects*; D015290:Second Messenger Systems / Q000502:physiology*
chemical_list: D015226:Dinucleoside Phosphates; D011983:Receptors, Purinergic; C020733:diadenosine tetraphosphate; D001920:Bradykinin; D002118:Calcium