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Muscarinic Cholinergic Stimulation of Exogenous Phosphatidylinositol Hydrolysis Is Regulated by Guanine Nucleotides in Rabbit Brain Cortical Membranes
Author(s) -
Carter Helen R.,
Fain John N.
Publication year - 1991
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1991.tb02059.x
Subject(s) - cholinergic , phosphatidylinositol , muscarinic acetylcholine receptor , stimulation , membrane , nucleotide , guanine , chemistry , rabbit (cipher) , neuroscience , biochemistry , microbiology and biotechnology , biology , signal transduction , receptor , computer science , gene , computer security
Rabbit brain cortical membranes, which have been extracted with 2 M KCl, hydrolyze exogenously added [ 3 H]phosphatidylinositol ([ 3 H]PI) in a guanine nucleotide‐and carbachol‐dependent manner. Both oxotremorine‐M and carbachol are full agonists with EC 50 values of 8 and 73 μ M , respectively. Pirenzepine and atropine inhibit carbacholstimulated [ 3 H]PI hydrolysis. The hydrolysis‐resistant guanine nucleotide analog guanosine 5′‐ O (3‐thiotriphosphate) (GTPγS) is the most potent in supporting carbachol‐stimu‐lated hydrolysis of PI. There is no effect of carbachol in the absence of guanine nucleotides or in the presence of 100 μ M adenosine 5′‐ O (3‐thiotriphosphate), adenosine‐5′‐(β,γ‐imido)triphosphate, or sodium pyrophosphate. Guanylyl‐5′‐(β,γ‐imido)triphosphate [Gpp(NH)p] in the presence of carbachol also stimulates PI hydrolysis although much less than that seen with GTP‐γS. GDP and Gpp(NH)p are potent antagonists of the GTPγS‐dependent carbachol response. Optimal stimulation by carbachol and GTP7S was observed at 0.3–1 μ M free Ca 2+ and 6mM MgCl 2 . Limited trypsinization resulted in loss of receptor‐regulated PI breakdown and a slight decrease in basal activity. These results demonstrate that phospholipase C hydrolysis of exogenous PI by rabbit cortical membranes may be stimulated by carbachol in a guanine nucleotide‐dependent manner.