Article date: 1988/11/15
PubMed ID: 2904266
Journal name: Biochemical pharmacology (ISSN: 0006-2952)
The relative roles of protein kinase C in regulating excitatory amino acid-, cholinoceptor-, and adrenoceptor-stimulated phosphoinositide hydrolysis were studied. Slices of rat hippocampus were prelabeled with [3H]-myo-inositol, and agonist-induced [3H]-phosphoinositide hydrolysis was measured by the formation of [3H]-inositol monophosphate ([3H]-IP) in the presence of lithium ion. Activation of protein kinase C with phorbol 12,13-dibutyrate (PDB) (10(-6) M) completely inhibited ibotenate (IBO) (10(-3) M)-induced [3H]-phosphoinositide hydrolysis. Half-maximal inhibition was observed at about 10(-7) M PDB. Higher concentrations of PDB were required to inhibit stimulation of [3H]-IP by either carbachol (CARB) (10(-3) M) or norepinephrine (NE) (10(-4) M, and only partial inhibition could be attained. Preincubation with staurosporine (STAURO) (10(-5) M) or 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) (10(-4) M), inhibitors of protein kinase C, potentiated IBO- but not CARB- or NE-induced stimulation of [3H]-IP. PDB inhibition of IBO- or NE-stimulated [3H]-phosphoinositide hydrolysis was reversed by co-addition of STAURO or H-7. In the case of IBO + STAURO, this reversal was to the potentiated level observed with STAURO alone. Enhanced agonist stimulation and reversal of PDB inhibition were also produced by STAURO when [3H]-phosphoinositide hydrolysis was stimulated by either L-glutamate or quisqualate. These experiments show that direct activation of protein kinase C by PDB leads to inhibition of phosphoinositide hydrolysis mediated by excitatory amino acid receptors, cholinoceptors, or adrenoceptors. However, the enhanced agonist-stimulated phosphoinositide hydrolysis elicited by inhibitors of protein kinase C suggests that, when protein kinase C is indirectly activated, only excitatory amino acids rapidly inhibit further receptor-coupling.
Author List: Schoepp D D, Johnson B G
Publication Types: Journal Article
Substances mentioned in the article: Alkaloids; Amino Acids; Glutamates; Oxadiazoles; Phosphatidylinositols; Homocysteine; homocysteic acid; Ibotenic Acid; Phorbol 12,13-Dibutyrate; Glutamic Acid; Quisqualic Acid; Carbachol; Protein Kinase C; Staurosporine; Norepinephrine;
Mesh terms: Alkaloids/pharmacology; Amino Acids/pharmacology; Animals; Carbachol/pharmacology; Enzyme Activation; Glutamates/pharmacology; Glutamic Acid; Hippocampus/drug effects; Homocysteine/analogs & derivatives; Ibotenic Acid/pharmacology; Male; Norepinephrine/pharmacology; Oxadiazoles/pharmacology; Phorbol 12,13-Dibutyrate/pharmacology; Phosphatidylinositols/metabolism; Protein Kinase C/metabolism; Quisqualic Acid; Rats; Rats, Inbred Strains; Staurosporine;