Rise in cytosolic Ca2+ concentration induced by P2‐purinoceptor activation in isolated myocytes from the rat gastrointestinal tract

• Published in: British journal of pharmacology 1996-03, Vol.117 (5), p.775-780
• Main Authors: Blottière, Hervé M., Loirand, Gervaise, Pacaud, Pierre
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - analogs & derivatives; Animals; ATP; Biological and medical sciences; Calcium - metabolism; Cells, Cultured; Dose-Response Relationship, Drug; free cytosolic calcium; Fundamental and applied biological sciences. Psychology; Intestinal smooth muscle; Intestine, Small - drug effects; Intestine. Mesentery; Muscle, Smooth - drug effects; Muscle, Smooth - metabolism; P2‐purinoceptors; Purinergic P2 Receptor Agonists; Rats; Rats, Wistar; Vertebrates: digestive system
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1111/j.1476-5381.1996.tb15259.x

1 The changes in the free cytosolic Ca2+ concentration ([Ca2+]i) in response to agonists of P2‐purinoceptors were studied in myocytes isolated from the longitudinal muscle layer of different regions of the rat gastrointestinal tract (stomach, jejunum, ileum, caecum and colon). [Ca2+]i was estimated by emission from the fluorescent dye, indo‐1. 2 ATP and the P2Y‐purinoceptor agonist, 2‐methylthio‐ATP (2‐MeSATP), transiently increased [Ca2+]i in single myocytes from all segments of the gastrointestinal tract, whereas α,β‐methylene‐ATP, a P2X‐purinoceptor agonist, had no effect. 3 The rise in [Ca2+]i induced by ATP and 2‐MeSATP was maintained in Ca2+‐free solution but was abolished by depletion of the intracellular store with thapsigargin (1 μm). 4 Single myocytes from stomach, caecum and colon also responded to UTP by a transient increase in [Ca2+]i. 5 Individual myocytes responded to ATP, 2‐MeSATP and UTP in a nearly all‐or‐nothing manner. The increasing of agonist concentration enhanced the number of responding cells but did not increase the amplitude of the [Ca2+]i rise. 6 These results suggest that myocytes from the longitudinal layer of gastrointestinal muscle do not possess functional P2X‐purinoceptors and that agonists of P2Y and P2U‐purinoceptors induced a rise in [Ca2+]i, probably via an all‐or‐nothing mobilization of Ca2+ from intracellular stores.