title: GTP increases airway muscarinic antagonist binding sites: an effect regulated by Mg2+.
abstract: Using [3H]QNB, we demonstrated that GTP and Gpp(NH)p increased muscarinic receptor high affinity sites in bovine tracheal muscle preparations; however, neither the dissociation constant of [3H]QNB binding sites nor pulmonary beta-adrenergic receptor sites was altered. The GTP effect on increasing the receptor sites was relatively small (16%), sensitive (ED50 0.48 microM) and specific (Gpp(NH)p greater than GTP = GDP greater than GMP much greater than ATP). Mg2+ potentiated this increase by up to 94.8%, whereas Na+, K+ and Ca2+ had no such effect.
mesh_terms: D000818:Animals; D002417:Cattle; D006160:Guanosine Triphosphate / Q000494:pharmacology*; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D066298:In Vitro Techniques; D008274:Magnesium / Q000502:physiology*; D008566:Membranes / Q000378:metabolism; D009130:Muscle, Smooth / Q000187:drug effects; D010276:Parasympatholytics / Q000378:metabolism; D011813:Quinuclidinyl Benzilate / Q000378:metabolism; D011950:Receptors, Cholinergic / Q000187:drug effects*; D011976:Receptors, Muscarinic / Q000187:drug effects* / Q000378:metabolism; D014132:Trachea / Q000378:metabolism
chemical_list: D010276:Parasympatholytics; D011950:Receptors, Cholinergic; D011976:Receptors, Muscarinic; D006165:Guanylyl Imidodiphosphate; D011813:Quinuclidinyl Benzilate; D006160:Guanosine Triphosphate; D008274:Magnesium