Ca2+ responses to ATP via purinoceptors in the early embryonic chick retina.
1. The action of adenosine triphosphate on cytoplasmic Ca2+ concentration ([Ca2+]i) was studied in the retinal cell of early embryonic chicks with fura-2 fluorescence measurements. The fluorescence was measured from the whole neural retina dissected from chick embryos at embryonic day three (E3). 2. Bath application of ATP (> or = 30 microM; EC50, 128 microM) raised [Ca2+]i by the release of Ca2+ from intracellular Ca2+ stores, since the Ca2+ response to ATP occurred even in a Ca(2+)-free medium. 3. The Ca2+ response to ATP was mediated by P2U purinoceptors. An agonist for P2U purinoceptors, uridine triphosphate (UTP), evoked Ca2+ rises more potently (> or = 3 microM; EC50, 24 microM) than ATP. Agonists for P2X purinoceptors, alpha, beta-methylene ATP and beta, gamma-methylene ATP, or an agonist for P2Y purinoceptors, 2-methylthio ATP (500 microM each), caused no Ca2+ response. Suramin (100 microM) and Reactive Blue 2 (50 microM) almost completely blocked the Ca2+, responses to 500 microM ATP and 200 microM UTP. 4. The developmental profile of the Ca2+ response to ATP was studied from E3 to E13. The Ca2+ response to ATP was largest at E3, drastically declined towards E8 and decreased further until E11-13. 5. These results suggest that the Ca2+ mobilization by ATP via P2U purinoceptors is characteristic of early embryonic retinal cells.
Sugioka
M
M
Department of Physiology, Osaka University Medical School, Suita, Japan.
Fukuda
Y
Y
Yamashita
M
M
D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002642:Chick Embryo; D005456:Fluorescent Dyes; D016257:Fura-2; D058913:Purinergic Agonists; D058914:Purinergic Antagonists; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D011983:Receptors, Purinergic / Q000502:physiology*; D018048:Receptors, Purinergic P2 / Q000502:physiology; D012160:Retina / Q000196:embryology / Q000378:metabolism*; D013569:Synapses / Q000502:physiology; D014544:Uridine Triphosphate / Q000037:antagonists & inhibitors / Q000494:pharmacology
D005456:Fluorescent Dyes; D058913:Purinergic Agonists; D058914:Purinergic Antagonists; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D011983:Receptors, Purinergic; D018048:Receptors, Purinergic P2; D000255:Adenosine Triphosphate; D002118:Calcium; D016257:Fura-2; D014544:Uridine Triphosphate