Pertussis toxin-sensitive and pertussis toxin-insensitive inhibition of parietal cell response to GLP-1 and histamine.
We have recently shown that in rat parietal cells the glucagon-like peptide 1 (GLP-1) variants 7-36 amide, 1-37, and 1-36 amide stimulate H+ production as indirectly measured by [14C]aminopyrine (AP) accumulation. This response to the GLP-1 peptides was intracellularly mediated by activation of adenylate cyclase and by adenosine 3',5'-cyclic monophosphate (cAMP) as second messenger. In the present study, we compared prostaglandin (PG)E2, somatostatin, and the protein kinase A antagonist Rp-adenosine-3',5'-monophosphorothioate (Rp-cAMPS) with respect to their inhibitory effects on parietal cell function induced by GLP-1 or histamine. PGE2 and somatostatin noncompetitively inhibited AP accumulation and cAMP production in response to the GLP-1 variants and histamine (IC50): [mean inhibitory concn 5 x 10(-9) M PGE2; 3 x 10(-7) somatostatin]; at their maximal concentrations PGE2 (10(-7) M) and somatostatin (10(-6) M) caused 85 and 65% inhibition, respectively. Treatment with pertussis toxin (PT; 250 ng/ml; 4 h) reversed the inhibitory effect of PGE2 and somatostatin on AP accumulation and cAMP production. At 2 x 10(-3) M (IC50: 3 x 10(-4) M) Rp-cAMPS completely inhibited AP accumulation induced by the GLP-1 variants or histamine; this effect was insensitive to PT. Specificity of Rp-cAMPs as protein kinase A inhibitor is suggested by inhibition of AP accumulation in response to Sp-cAMPS and N6,O2-dibutyryl adenosine 3',5'-cyclic phosphate sodium, and forskolin, activators of protein kinase A and adenylate cyclase, respectively. We conclude that the parietal cell responses to GLP-1 and histamine are inhibited by identical mechanisms. Effects of PGE2 and somatostatin are mediated by the PT-sensitive subunit of adenylate cyclase Gi, whereas Rp-cAMPS interferes with cAMP-dependent mechanisms that are insensitive to PT.
Department of Medicine II, Technical University of Munich, Federal Republic of Germany.
W
W
Schepp
J
J
Schmidtler
K
K
Dehne
V
V
Schusdziarra
M
M
Classen
D037361:Adenylate Cyclase Toxin; D000632:Aminopyrine / Q000378:metabolism; D000818:Animals; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000494:pharmacology; D004351:Drug Resistance; D005934:Glucagon / Q000494:pharmacology*; D052216:Glucagon-Like Peptide 1; D006632:Histamine / Q000494:pharmacology*; D009994:Osmolar Concentration; D010295:Parietal Cells, Gastric / Q000187:drug effects*; D010446:Peptide Fragments / Q000494:pharmacology*; D037342:Pertussis Toxin; D047428:Protein Kinase Inhibitors; D011498:Protein Precursors / Q000494:pharmacology*; D013004:Somatostatin / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D037361:Adenylate Cyclase Toxin; D010446:Peptide Fragments; D047428:Protein Kinase Inhibitors; D011498:Protein Precursors; D013873:Thionucleotides; D010566:Virulence Factors, Bordetella; D000632:Aminopyrine; C016957:adenosine-3',5'-cyclic phosphorothioate; D013004:Somatostatin; D006632:Histamine; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D000242:Cyclic AMP; D037342:Pertussis Toxin; D015232:Dinoprostone