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Blockade of Receptor‐Mediated Cyclic GMP Formation by Hydroxyeicosatetraenoic Acid
Author(s) -
McKinney Michael
Publication year - 1987
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.1471-4159.1987.tb02870.x
Subject(s) - muscarinic acetylcholine receptor , carbachol , chemistry , muscarinic acetylcholine receptor m3 , endocrinology , arachidonic acid , receptor , lipoxygenase , medicine , muscarinic acetylcholine receptor m1 , biochemistry , biology , enzyme
Receptor‐mediated cyclic GMP formation in N1E‐115 murine neuroblastoma cells appears to involve oxidative metabolism of arachidonic acid. Evidence in support of this includes the blockade of this response by lipoxygenase inhibitors, e.g., eicosatetraynoic acid (ETYA) or other metabolic perturbants, e.g., methylene blue. It was recently discovered that the lipoxygenase products 15‐hydroxyeicosatetraenoic (15‐HETE) acid and 12‐HETE, like ETYA, were inhibitors of M 1 muscarinic receptor‐mediated cyclic GMP formation. In the present report, the effects of monoHETEs are explored in more detail, particularly with regard to the function of the muscarinic receptor. Like 12‐HETE and 15‐HETE (IC 50 = 13 and 11 μ M , respectively), 5‐HETE inhibited the cyclic GMP response to the muscarinic receptor (IC 50 = 10 μ M ). All three of these monoHETEs were shown also to be inhibitors of the cyclic GMP responses to receptors stimulated by carbachol, histamine, thrombin, neurotensin, and bradykinin. 15‐HETE was shown to inhibit the muscarinic receptor‐mediated response in a complex manner (apparent noncompetitive and uncompetitive components; IC 50 = 18 and 2 μ M , respectively). 15‐HETE did not inhibit either the M 1 muscarinic receptor‐stimulated release of [ 3 H]inositol phosphates from cellular phospholipids or the M 2 muscarinic receptor‐mediated inhibition of hormone (prostaglandin E 1 )‐induced AMP formation. It seemed possible that the monoHETEs could enter into biochemical pathways for arachidonate in N1E‐115 cells. [ 3 H]Arachidonate and the three [ 3 H]‐monoHETEs all rapidly labeled the membrane lipids of intact NIE‐115 cells, with each [ 3 H]eicosanoid producing a unique labeling profile. [ 3 H] 15‐HETE labeling was noteworthy in that 85% of the label found in the phospholipids was in phosphatidylinositol (PI; t 1/2 to steady state = 3 min). Exogenous 15‐HETE inhibited the labeling of PI by [ 3 H]‐arachidonate (IC 50 = 28 μ M ) and elevated unesterified [ 3 H]‐arachidonate levels. Thus, the mechanism of blockade of receptor‐mediated cyclic GMP responses by monoHETEs is likely to be more complex than the simple inhibition of cytosolic mechanisms, e.g., generation of a putative second messenger by lipoxygenase, and may involve also alterations of membrane function accompanying the redistribution of esterified arachidonate.