title: Leukotriene and purinergic receptors are involved in the hyperpolarizing effect of glucagon in liver cells.
abstract: The pancreatic hormone glucagon hyperpolarizes the liver cell membrane. In the present study, we investigated the cellular signalling pathway of glucagon-induced hyperpolarization of liver cells by using the conventional microelectrode method. The membrane potential was recorded in superficial liver cells of superfused mouse liver slices. In the presence of the K+ channel blockers tetraethylammonium (TEA, 1 mmol/l) and Ba2+ (BaCl2, 5 mmol/l) and the blocker of the Na+/K+ ATPase, ouabain (1 mmol/l), no glucagon-induced hyperpolarization was observed confirming previous findings. The hyperpolarizing effect of glucagon was abolished by the leukotriene B4 receptor antagonist CP 195543 (0.1 mmol/l) and the purinergic receptor antagonist PPADS (5 micromol/l). ATPgammaS (10 micromol/l), a non-hydrolyzable ATP analogue, induced a hyperpolarization of the liver cell membrane similar to glucagon. U 73122 (1 micromol/l), a blocker of phospholipase C, prevented both the glucagon- and ATPgammaS-induced hyperpolarization. These findings suggest that glucagon affects the hepatic membrane potential partly by inducing the formation and release of leukotrienes and release of ATP acting on purinergic receptors of the liver cell membrane.
authors.affiliation: Institute of Veterinary Physiology, Vetsuisse Faculty University of Zurich, Winterthurerstrasse 260, 8057 Zurich, Switzerland.
authors.forename: Lisa
authors.initials: L
authors.lastname: Fischer
authors.forename: Silke
authors.initials: S
authors.lastname: Haag-Diergarten
authors.forename: Erwin
authors.initials: E
authors.lastname: Scharrer
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Lutz
mesh_terms: D000818:Animals; D005260:Female; D005934:Glucagon / Q000378:metabolism*; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D026902:Potassium Channel Blockers / Q000494:pharmacology; D058914:Purinergic Antagonists; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D018077:Receptors, Leukotriene / Q000378:metabolism*; D011983:Receptors, Purinergic / Q000378:metabolism*
chemical_list: D026902:Potassium Channel Blockers; D058914:Purinergic Antagonists; D018077:Receptors, Leukotriene; D011983:Receptors, Purinergic; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; D005934:Glucagon