Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.6.1.2 (guanylate cyclase)
 8,497 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Inhibitors of arachidonate metabolism and perturbants of the oxidation-reduction state of the cell were employed to develop a pharmacologic profile for muscarinic receptor-mediated cyclic GMP formation in murine neuroblastoma cells (clone N1E-115). Several lipoxygenase inhibitors [eicosatetraynoic acid (ETYA), nordihydroguaiaretic acid (NDGA), FPL 57231, FPL 55712, BW755c, propylgallate, and AA861] blocked the elevation of [3H]cyclic GMP induced by muscarinic receptor activation. The cyclooxygenase inhibitors indomethacin and ibuprofen were two orders of magnitude less potent in blocking the muscarinic receptor-mediated [3H]cyclic GMP response than in blocking cyclooxygenase in other systems. ETYA and NDGA did not affect the muscarinic inhibition of the prostaglandin E1-mediated increases in [3H]cyclic AMP levels in N1E-115 cells. ETYA did not have a reproducible effect on the muscarinic receptor-induced release of inositol phosphates. Thus, these lipoxygenase inhibitors appeared to be selective for the effector system coupled to the low-affinity muscarinic agonist-receptor conformation, i.e. that which induces cyclic GMP formation. Other effective inhibitors of the cyclic GMP response were methylene blue, catalase, bromphenacyl bromide, retinal, dithiothreitol, quinacrine, and oxidized glutathione. The antioxidant alpha-tocopherol in the concentration range of 100 microM to 1 mM potentiated the receptor response. Arachidonic acid itself was an inhibitor of the muscarinic receptor-mediated cyclic GMP response (IC50 = 45 microM). Linoleic acid and oleic acid were less potent (IC50 = 130 and 190 microM, respectively), and stearic acid was ineffective. When arachidonic acid was air-oxidized, its inhibitory potency was increased 10-fold. Most but not all of the spontaneously-produced oxidative metabolites, separable by reverse-phase high pressure liquid chromatography, were inhibitory to the receptor response. Enzymatically synthesized 12-hydroxyeicosatetraenoic acid and 15-hydroxyeicosatetraenoic acid inhibited the muscarinic receptor [3H]cyclic GMP response, with IC50 values of 17 and 8 microM respectively. Catalase was effective in blocking the muscarinic cyclic GMP response (IC50 = 5 microM) while having no effect on either the muscarinic receptor-induced inositol phosphate release or the reduction of cyclic AMP levels. Thus, the effector system for increasing cyclic GMP in these cells displays may of the expected characteristics for the involvement of a lipoxygenase or a related enzyme that oxidatively metabolizes arachidonate in order to activate the guanylate cyclase.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Blockade of N1E-115 murine neuroblastoma muscarinic receptor function by agents that affect the metabolism of arachidonic acid. 301 48

Arachidonic acid is converted by blood platelets into thromboxane A2 (TXA2) and 12-hydroxyeicosatetraenoic acid (12-OH-C20:4). TXA2 causes platelet aggregation, but the physiological role of 12-OH-C20:4 on blood platelets is not known. The formation of 12-OH-C20:4 by washed platelets can be inhibited by eicosatetraynoic acid at a concentration of 0.7 mumol/l; TXA2-formation is not yet influenced at this low inhibitor concentration. Under these conditions, the irreversible 1-14C arachidonic acid-induced blood platelet aggregation is converted into a reversible type of aggregation. Similar results are obtained by addition of any long-chain fatty acid (20-30 mumol/l), including 12-OH-C20:4 and arachidonic acid, as well as by addition of sulfhydryl reagents. However, in these experiments no inhibition of the arachidonic acid conversion is observed. The results can be explained by a "sticking together" of the blood platelets caused by 12-OH-C20:4 generation. This effect is based on the same principle as that of the chemotactic effect of 12-OH-C20:4 on leucocytes as described by Turner et al. (Nature 257; 680-681, 1975). The explanation is supported by experiments with platelets obtained after ingestion of aspirin. ADP-induced reversible aggregation of three platelets becomes irreversible after addition of arachidonic acid. Irreversible platelet aggregation occurs only during endogenous 12-OH-C20:4 generation in consequence of a "sticking-together" process. This process coincides with a stimulation of the platelet guanylate cyclase.
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PMID:The role of arachidonate lipoxygenase and fatty acids during irreversible blood platelet aggregation in vitro. 678 28