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Receptor‐Coupled Phosphoinositide Hydrolysis in Human Retinal Pigment Epithelium
Author(s) -
Feldman Eva L.,
Randolph Ann E.,
Johnston Gregory C.,
DelMonte Monte A.,
Greene Douglas A.
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.tb03471.x
Subject(s) - carbachol , histamine , pirenzepine , retinal pigment epithelium , muscarinic acetylcholine receptor , chemistry , endocrinology , histaminergic , inositol , medicine , inositol phosphate , intracellular , extracellular , receptor , biology , biochemistry , retinal
Carbachol and histamine stimulated phosphoinositide (PPI) hydrolysis in cultured human retinal pigment epithelium (RPE), as reflected by an accumulation of 3 H‐inositol phosphates in the presence of 10 m M Li + . Carbachol increased PPI hydrolysis to greater than 600% of basal with an EC 50 of 60 μ M ; stimulation was linear up to 60 min. This activation likely occurred via the M 3 muscarinic cholinergic receptor based on the IC 50 values for 4‐diphenylacetoxy‐ N ‐methylpiperidine methiodide (0.47 n M ), pirenzepine (280 n M ), and 11‐[[2‐[(diethylamino)methyl]‐1‐piperidinyl]‐acetyl]‐5,11‐dihydro‐6 H ‐pyrido[2,3‐ b ][1,4]benzodiazepin‐6‐one (1.4 μ M ). Carbachol‐mediated PPI hydrolysis was decreased by 80% in the absence of extracellular Ca 2+ . Histamine stimulated PPI turnover in a linear manner by 180% with an EC 50 of 20 μ M by the H 1 histaminergic receptor. Serotonin, glutamate, norepinephrine, and dopamine were inactive. In human RPE, the resting cytoplasmic Ca 2+ concentration, as determined by fura‐2 fluorescence, was 138 ± 24 n M . On the addition of carbachol, there was a 180% increase in peak intracellular Ca 2+ ; addition of histamine increased intracellular Ca 2+ by 187%. These results suggest receptor‐mediated, inositol lipid hydrolysis is coupled to intracellular Ca 2+ flux in human RPE.