title: Stimulation of the P2Y purinergic receptor on type 1 astroglia results in inositol phosphate formation and calcium mobilization.
abstract: Cultured astroglia express purinergic receptors that initiate phosphoinositide metabolism and calcium mobilization. Experiments were conducted to characterize the purinergic receptor subtype on type 1 astroglia responsible for stimulation these second-messenger systems. Inositol phosphate (IP) accumulation and calcium mobilization were measured after stimulation with ATP or purinergic receptor subtype-selective ATP analogues. ATP (10(-5) M) increased IP accumulation severalfold. Dose-effect assays monitoring astroglial IP accumulation revealed the order of potency that defines the P2Y receptor: 2-methylthioadenosine 5'-triphosphate greater than ATP greater than alpha beta-methyleneadenosine 5'-triphosphate greater than beta gamma-methyleneadenosine 5'-triphosphate. The influence of ATP on intracellular calcium levels in individual type 1 astroglia was examined using the calcium indicator dye, fura-2. Dose-effect experiments indicated that ATP was equally potent for generating inositol phosphates and increasing cellular calcium. The most prevalent response (87% of total responses) to ATP consisted of a rapid increase in calcium to a peak level that was approximately five times greater than the prestimulation level. This peak was followed by a decline to a plateau level that was significantly above baseline. This plateau phase of the calcium increase was maintained for at least 5 min in the presence of ATP and was dependent on external calcium. Many (23%) astroglia exhibited spontaneous calcium oscillations whose frequency and magnitude increased after the addition of 10(-5) M ATP. Immunocytochemical staining indicated that the responses occurred in glial fibrillary acidic protein positive cells. We conclude that type 1 astroglia express the P2Y purinergic receptor which regulates IP production and calcium mobilization.
authors.affiliation: Pharmacology Department, University of North Carolina, Chapel Hill 27599.
authors.forename: C H
authors.initials: CH
authors.lastname: Kastritsis
authors.forename: A K
authors.initials: AK
authors.lastname: Salm
authors.forename: K
authors.initials: K
authors.lastname: McCarthy
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005110:Extracellular Space / Q000378:metabolism; D007295:Inositol Phosphates / Q000096:biosynthesis*; D007425:Intracellular Membranes / Q000378:metabolism; D009638:Norepinephrine / Q000494:pharmacology; D011983:Receptors, Purinergic / Q000378:metabolism*
chemical_list: D007295:Inositol Phosphates; D011983:Receptors, Purinergic; D000255:Adenosine Triphosphate; D002118:Calcium; D009638:Norepinephrine