RESUMEN
The magnetic susceptibility, high field magnetization, and specific heat measurements of Cu3(CO3)2(OH)2, which is a model substance for the frustrating diamond spin chain model, have been performed using single crystals. Two broad peaks are observed at around 20 and 5 K in both magnetic susceptibility and specific heat results. The magnetization curve has a clear plateau at one third of the saturation magnetization. The experimental results are examined in terms of theoretical expectations based on exact diagonalization and density matrix renormalization group methods. An origin of magnetic anisotropy is also discussed.
RESUMEN
2-Arachidonoylglycerol was found to inhibit the depolarization-induced increase in [Ca2+]i in NG108-15 cells differentiated with prostaglandin E1 and theophylline in a dose-dependent manner. Such an effect appears to be rather specific to polyunsaturated fatty acid-containing monoacylglycerols such as 2-arachidonoylglycerol. Neither 2-palmitoylglycerol nor free arachidonic acid exhibited appreciable inhibitory activity. These observations raise the possibility that 2-arachidonoylglycerol attenuates the increase in [Ca2+]i, thereby modulating several neural functions in this type of cell.
Asunto(s)
Ácidos Araquidónicos , Calcio/metabolismo , Glioma/metabolismo , Glicéridos/farmacología , Neuroblastoma/metabolismo , Neurotransmisores/farmacología , Endocannabinoides , Glioma/patología , Células Híbridas , Neuroblastoma/patología , Células Tumorales CultivadasRESUMEN
Low concentrations of 2-arachidonoylglycerol were found to induce rapid, transient elevation of intracellular free Ca2+ in NG108-15 cells (EC50 was 150 nM). Free arachidonic acid, 2-palmitoylglycerol, 2-oleoylglycerol, 2-linoleoylglycerol and 2-docosahexaenoylglycerol were inactive. Anandamide acted as a partial agonist. Importantly, desensitization was observed upon sequential challenge with 2-arachidonoylglycerol. Furthermore, cross-desensitization was observed between 2-arachidonoylglycerol and WIN 55212-2, a cannabinoid receptor agonist. Pretreatment of the cells with SR141716A, a cannabinoid receptor antagonist, abolished the activities of both 2-arachidonoylglycerol and WIN 55212-2. These results strongly suggest that 2-arachidonoylglycerol and WIN 55212-2 bind to a common cannabinoid receptor to elicit cellular responses and that 2-arachidonoylglycerol has some physiological role in nervous tissues.
Asunto(s)
Calcio/metabolismo , Glicéridos/farmacología , Neuronas/efectos de los fármacos , Receptores de Droga/metabolismo , Ácidos Araquidónicos/farmacología , Benzoxazinas , Cannabinoides/metabolismo , Relación Dosis-Respuesta a Droga , Interacciones Farmacológicas , Endocannabinoides , Glioma , Glicéridos/química , Células Híbridas , Ligandos , Morfolinas/farmacología , Naftalenos/farmacología , Neuroblastoma , Piperidinas/farmacología , Factor de Activación Plaquetaria/farmacología , Alcamidas Poliinsaturadas , Pirazoles/farmacología , Receptores de Cannabinoides , Receptores de Droga/agonistas , Receptores de Droga/antagonistas & inhibidores , RimonabantRESUMEN
The enzymatic synthesis of a novel sleep-inducing lipid, oleamide (cis-9,10-octadecenoamide), was studied using rat brain subcellular fractions as enzyme sources. We found that oleamide was formed from oleic acid and ammonia on incubation with a brain homogenate. The enzyme activity catalyzing the formation of oleamide from oleic acid and ammonia was highest in the microsomal fraction among the subcellular fractions. Boiled microsomes did not exhibit appreciable enzyme activity. These results strongly suggest that oleamide can be synthesized enzymatically in the brains of stimulated animals.
Asunto(s)
Encéfalo/enzimología , Microsomas/enzimología , Ácidos Oléicos/biosíntesis , Adenosina Trifosfato/farmacología , Amoníaco/metabolismo , Animales , Coenzima A/farmacología , Glutamina/metabolismo , Cinética , Ácido Oléico/metabolismo , Ratas , Fracciones Subcelulares/enzimologíaRESUMEN
The effects of N-arachidonoylethanolamine (anandamide) and related compounds on the binding of [3H]CP55940 to rat brain synaptosomes were examined. Anandamide was shown to inhibit competitively the specific binding of [3H]CP55940 to synaptosomal membranes. The Ki value was 89 nM. In contrast, N-acylethanolamines containing saturated or monoenoic fatty acids did not exhibit high binding affinity. Several structural analogues of anandamide showed some binding activity. Among them, 2-arachidonoylglycerol is noteworthy because of its occurrence in mammalian tissues. A biosynthetic study indicated that anandamide can be synthesized via two separate synthetic pathways. The first is synthesis from free arachidonic acid and ethanolamine, and the second is the formation of N-arachidonoyl phosphatidylethanolamine (PE) from diarachidonoyl phospholipids and PE and the subsequent enzymatic release of N-arachidonoylethanolamine. The latter pathway appears to explain very well the fatty acid composition of N-acylethanolamines present in mammalian tissues.
Asunto(s)
Ácidos Araquidónicos/metabolismo , Metabolismo de los Lípidos , Sistema Nervioso/metabolismo , Receptores de Droga/metabolismo , Animales , Endocannabinoides , Humanos , Ligandos , Alcamidas Poliinsaturadas , Ratas , Receptores de Cannabinoides , Receptores de Droga/antagonistas & inhibidoresRESUMEN
The levels of N-arachidonoylethanolamine (anandamide), an endogenous cannabinoid-receptor ligand, and a relevant molecule, N-arachidonoylphosphatidylethanolamine (N-arachidonoylPtdEtn), in rat brain were investigated using a newly developed sensitive analytical method. We found that rat brain contains small but significant amounts of these two types of N-arachidonoyl lipids (4.3 pmol/g tissue and 50.2 pmol/g tissue, respectively). Then, we investigated how N-arachidonoylethanolamine (anandamide) is produced in the brain. We found that anandamide can be formed enzymatically via two separate synthetic pathways in the brain: enzymatic condensation of free arachidonic acid and ethanolamine; and formation of N-arachidonoylPtdEtn from PtdEtn and arachidonic acid esterified at the 1-position of phosphatidyl-choline (PtdCho), and subsequent release of anandamide from N-arachidonoylPtdEtn through the action of a phosphodiesterase. We confirmed that rat brain contains both the enzyme activities and lipid substrates involved in these reactions. Several lines of evidence strongly suggest that the second pathway, rather than the first one, meets the requirements and conditions for the synthesis of various species of N-acylethanolamine including anandamide in the brain.
Asunto(s)
Aciltransferasas/metabolismo , Ácido Araquidónico/metabolismo , Ácidos Araquidónicos/biosíntesis , Encéfalo/metabolismo , Etanolaminas/metabolismo , Microsomas/enzimología , Hidrolasas Diéster Fosfóricas/metabolismo , Animales , Cromatografía Líquida de Alta Presión , Endocannabinoides , Etanolamina , Etanolaminas/aislamiento & purificación , Ácidos Grasos no Esterificados/análisis , Cinética , Fosfatidilcolinas/química , Fosfatidilcolinas/metabolismo , Fosfatidiletanolaminas/química , Fosfatidiletanolaminas/metabolismo , Alcamidas Poliinsaturadas , RatasRESUMEN
Rat testis was shown to contain significant amounts of both N-acylethanolamine, including N-arachidonoylethanolamine (anandamide), and N-acylphosphatidylethanolamine (N-acylPE), including N-arachidonoylPE. The fatty acid profiles of the N-acyl moieties of the two classes resembled each other. We confirmed that testis microsomes contain a phosphodiesterase activity catalyzing the release of anandamide from N-arachidonoylPE. They also contain an enzyme activity catalyzing the transfer of arachidonic acid from the 1-position of diacylphospholipids to PE to form N-arachidonoylPE. These results suggest that the N-acylPE pathway is important in the synthesis of anandamide in this tissue.
Asunto(s)
Aciltransferasas/metabolismo , Ácidos Araquidónicos/biosíntesis , Calcio/farmacología , Microsomas/enzimología , Fosfatidiletanolaminas/metabolismo , Hidrolasas Diéster Fosfóricas/metabolismo , Receptores de Droga/metabolismo , Testículo/metabolismo , Animales , Ácido Araquidónico/metabolismo , Cannabinoides/biosíntesis , Endocannabinoides , Cinética , Masculino , Alcamidas Poliinsaturadas , Receptores de Cannabinoides , Especificidad por SustratoRESUMEN
When [14C]arachidonoyl-CoA was incubated with crude extracts of rat liver microsomes, [14C]arachidonic acid was incorporated into many proteins, suggesting that modification of these proteins with fatty acid, i.e. acylation, occurred. Using a [14C]arachidonyl-CoA labelling assay, 50 and 53 kDa proteins were purified from rat liver microsomes to near homogeneity by sequential chromatography on Red-Toyopearl, hydroxyapatite, heparin-Toyopearl, Blue-Toyopearl and UDP-hexanolamine-agarose. Acylation of the 50 and 53 kDa proteins occurred in the absence of any other protein, suggesting that these molecules catalyse autoacylation. The acylation was dependent on the length of the incubation period and the concentration of [14C]arachidonoyl-CoA. The 50 and 53 kDa proteins also had acyl-CoA-binding activity; initial rates of acyl-CoA binding and acylation were 0.25 and 0.004 min-1 respectively. The proteins also had weak but distinct acyl-CoA-hydrolysing activity (0.006 min-1). These results suggest that the proteins catalysed the sequential reactions of binding to acyl-CoA, autoacylation, and hydrolysis of fatty acid. N-terminal amino acid sequencing analysis showed these proteins to be UDP-glucuronosyltransferase (UDPGT) isoforms. UDPGT activity was inhibited by arachidonoyl-CoA. These results suggest that binding of acyl-CoA and acylation of UDPGT isoforms regulate the enzyme activities, implying a possible novel function for fatty acyl-CoA in glucuronidation, which is involved in the metabolism of drugs, steroids and bilirubin.