Stimulation of phospholipase C activity by norepinephrine, t-ACPD and bombesin in LA-N-2 cells.
The release of [3H]inositol phosphates from myo-[3H]inositol-prelabeled LA-N-2 cells was measured in the presence of beta-adrenoceptor, metabotropic glutamate and bombesin agonists. Norepinephrine and isoproterenol increased the formation of [3H]inositol phosphates in a dose-dependent manner, with an EC50 of 100 microM for norepinephrine and an EC50 of 5 microM for isoproterenol. These stimulations were abolished by propranolol, a beta-adrenoceptor antagonist, with an IC50 in the range of 50-55 microM for both norepinephrine and isoproterenol. The stimulation of [3H]inositol phosphate appearance occurred with varying concentrations of trans-1-amino-1,3-cyclopentanedicarboxylic acid (t-ACPD), a metabotropic glutamate receptor agonist. This release of [3H] inositol phosphates was blunted by its antagonist, 2-amino-3-phosphonopropionic acid (AP-3). Bombesin and neuromedin-B, a bombesin-like peptide, also increased the appearance of [3H]inositol phosphates. This was blunted by the antagonist [Tyr4, D-Phe12] bombesin. The appearance of [3H]inositol phosphates stimulated by t-ACPD was coupled through a cholera toxin-sensitive G-protein and the bombesin-stimulated appearance of [3H]inositol phosphates was coupled through a pertussis toxin-sensitive G-protein. The norepinephrine-stimulated appearance of [3H]inositol phosphates was toxin insensitive. The stimulation of the [3H]inositol phosphate appearance by these three agonists was protein kinase and Ca2+ independent.
Sorrentino
G
G
Istituto di Scienze Neurologiche, II Università degli Studi di Napoli, Italy.
Singh
I N
IN
Massarelli
R
R
Kanfer
J N
JN
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000409:Alanine / Q000031:analogs & derivatives / Q000494:pharmacology; D001839:Bombesin / Q000494:pharmacology*; D003515:Cycloleucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D007553:Isotope Labeling; D009447:Neuroblastoma / Q000201:enzymology / Q000378:metabolism; D015287:Neurokinin B / Q000031:analogs & derivatives / Q000494:pharmacology; D009498:Neurotoxins / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology; D018004:Receptors, Bombesin / Q000819:agonists; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists / Q000037:antagonists & inhibitors; D014316:Tritium; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism*
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D018691:Excitatory Amino Acid Antagonists; D007295:Inositol Phosphates; D009498:Neurotoxins; D018004:Receptors, Bombesin; D018094:Receptors, Metabotropic Glutamate; C000211:2-amino-3-phosphonopropionic acid; D003515:Cycloleucine; D014316:Tritium; C036361:1-amino-1,3-dicarboxycyclopentane; D015287:Neurokinin B; C038393:neuromedin B; D011433:Propranolol; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D007545:Isoproterenol; D000409:Alanine; D001839:Bombesin; D009638:Norepinephrine