Chick embryo muscarinic and purinergic receptors activate cytosolic Ca2+ via phosphatidylinositol metabolism.
In dissociated cells from chick embryos or from chick limb buds, acetylcholine (ACh) induced an increase in cellular levels of inositol 1,4,5-trisphosphate (Ins-P3) and of inositol 1,3,4,5-tetrakisphosphate (Ins-P4). The concentration of Ins-P3 was enhanced transiently, whereas the level of Ins-P4 remained elevated for at least 20 min after addition of ACh. In most cases the increase in Ins-P4 levels was more pronounced than that of Ins-P3 levels. The inhibition of the ACh-induced inositol-phosphate response by atropine (half-maximal inhibition at 10 nM) indicates the involvement of muscarinic receptors, which in chick embryo cells induce a transient rise and a following persistent elevation of cytosolic Ca2+ activity (G. Oettling et al. (1989) J. Dev. Physiol. 12, 85-94). Adenosine 5'-triphosphate (ATP) elicited a similar transient rise in cytosolic Ca2+ activity, however, without a subsequent plateau. ATP also caused an increase in inositol-oligophosphate levels. Thus, both muscarinic and purinergic receptors in chick embryo cells are coupled to phospholipase C. The enzymatically formed Ins-P3 mediates the release of Ca2+ from internal stores. The Ca2+ signal could be involved in embryonic cell migration during morphogenesis.
Lohmann
F
F
Anatomisches Institut, Universität Tübingen, Federal Republic of Germany.
Drews
U
U
Donié
F
F
Reiser
G
G
D000109:Acetylcholine / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology*; D002478:Cells, Cultured; D002642:Chick Embryo; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D007295:Inositol Phosphates / Q000378:metabolism*; D007700:Kinetics; D010716:Phosphatidylinositols / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology*; D011983:Receptors, Purinergic / Q000187:drug effects / Q000502:physiology*
D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D011976:Receptors, Muscarinic; D011983:Receptors, Purinergic; C081655:inositol-1,3,4,5-tetrakisphosphate; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D002217:Carbachol; D000109:Acetylcholine; D002118:Calcium