The stimulation of rat liver microsomal CDP-diacylglycerol formation by guanosine triphosphate

1980 ◽  
Vol 58 (10) ◽  
pp. 871-877 ◽  
Author(s):  
Robert G. Liteplo ◽  
Michael Sribney
Keyword(s):  
Phosphatidic Acid ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Covalent Modification ◽  
Rat Liver Microsomes ◽  
Dependent Manner ◽  
Temperature Dependent ◽  
Guanosine Triphosphate ◽  
Concentration Time ◽  
Stimulation Of

GTP has been found to markedly enhance the formation of CDP-diacylglycerol in rat liver microsomes. Neither GDP, GMP nor the nonhydrolyzable analogues of GTP increased the synthesis of the liponucleotide. The GTP stimulation of phosphatidate cytidylyltransferase activity is inhibited by EDTA and NaF. GTP enhances the activity of the enzyme in a concentration-, time-, and temperature-dependent manner and preincubation of rat liver microsomes with GTP produces a persistently activated phosphatidate cytidylyltransferase. GTP reduces the Km for phosphatidic acid, but has no effect on either the Km for CTP or the Vmax of the reaction. GTP, by stimulating the activity of the phosphatidate cytidylyltransferase, enhances the formation of phosphatidylinositol from CTP, phosphatidic acid, and inositol. Evidence is presented suggesting that the mechanism by which GTP stimulates the activity of the phosphatidate cytidylyltransferase involves a covalent modification of the enzyme itself or a protein intimately associated with the phosphatidate cytidylyltransferase.

scholarly journals 10-Undecynoic acid, an inhibitor of cytochrome P450 4A1, inhibits ethanolamine-specific phospholipid base exchange reaction in rat liver microsomes.

1999 ◽  
Vol 46 (1) ◽  
pp. 203-210 ◽  
Author(s):  
J Lenart ◽  
S Pikuła
Keyword(s):  
Endoplasmic Reticulum ◽  
Cytochrome P450 ◽  
Exchange Reaction ◽  
Rat Liver ◽  
Lauric Acid ◽  
Liver Microsomes ◽  
Specific Inhibitor ◽  
Rat Liver Microsomes ◽  
Dependent Manner ◽  
Base Exchange

1,12-Dodecanedioic acid, the end-product of omega-hydroxylation of lauric acid, stimulates in a concentration dependent manner, phosphatidylethanolamine synthesis via ethanolamine-specific phospholipid base exchange reaction in rat liver endoplasmic reticulum. On the other hand, administration to rats of 10-undecynoic acid, a specific inhibitor of omega-hydroxylation reaction catalyzed by cytochrome P450 4A1, inhibits the ethanolamine-specific phospholipid base exchange activity by 30%. This is accompanied by a small but significant decrease in phosphatidylethanolamine content in the endoplasmic reticulum and inhibition of cytochrome P450 4A1. On the basis of these results it can be proposed that a functional relationship between cytochrome P450 4A1 and phosphatidylethanolamine synthesis exists in rat liver. Cytochrome P450 4A1 modulates the cellular level of lauric acid, an inhibitor of phospholipid synthesis. In turn, ethanolamine-specific phospholipid base exchange reaction provides molecular species of phospholipids, containing mainly long-chain polyunsaturated fatty acid moieties, required for the optimal activity of cytochrome P450 4A1.

scholarly journals Cytochemical analysis of the reconstitution of endoplasmic reticulum after microinjection of rat liver microsomes into Xenopus oocytes.

1988 ◽  
Vol 36 (10) ◽  
pp. 1263-1273 ◽  
Author(s):  
J Paiement ◽  
F W Kan ◽  
J Lanoix ◽  
M Blain
Keyword(s):  
Endoplasmic Reticulum ◽  
Rat Liver ◽  
Smooth Endoplasmic Reticulum ◽  
Light And Electron Microscopy ◽  
Liver Microsomes ◽  
Heat Denaturation ◽  
Rat Liver Microsomes ◽  
Dependent Manner ◽  
Lysosomal Activity

Fragments of rough and smooth endoplasmic reticulum purified from rat liver were injected into Xenopus oocyte cytoplasm. Light and electron microscopy, cytochemistry, immunocytochemistry, and enzyme assay were employed to determine the fate of heterologous membranes in the host cytoplasm. The in vivo-incubated microsomes disappeared in a time-dependent manner. Within 3 hr, rough microsomes were replaced by flattened ER cisternae and smooth microsomes were replaced by a network of anastomosing tubules. Polyclonal antibodies against rat liver microsomes and protein A-gold complexes were applied to glycol methacrylate sections of microinjected oocytes. Specific labeling was observed over discrete rough and smooth ER cisternae 3 hr after microinjection. Endogenous ER was not labeled by this technique, and label was not observed when sections were treated with pre-immune antibodies. Diaminobenzidene cytochemistry of microinjected rat lacrimal gland microsomes revealed enzyme activity in heterologous microsomes after 3 hr of in vivo incubation. Control injected microsomes (inactivated by heat denaturation) became associated with autophagic vacuoles, coincident with changes in lysosomal activity. Freshly isolated un-denatured microsomes did not provoke changes in lysosomal activity, and glucose-6-phosphatase activity associated with microinjected membranes could be detected 21 hr after in vivo incubation. Since rat liver microsomes reconstitute after in vivo incubation into cytoplasmic structures resembling those from which they were derived, we conclude that the microinjected membrane fragments act as templates for their own three-dimensional organization.

scholarly journals Ring-Oxidative Biotransformation and Drug Interactions of Propofol in the Livers of Rats

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Yu-Ting Tai ◽  
Yi-Ling Lin ◽  
Chia-Chen Chang ◽  
Yih-Giun Cherng ◽  
Ming-Jaw Don ◽  
...  
Keyword(s):  
Liquid Chromatography ◽  
Drug Interactions ◽  
Rat Liver ◽  
Oxidative Metabolism ◽  
Critical Role ◽  
Liver Microsomes ◽  
Anesthetic Agent ◽  
Rat Liver Microsomes ◽  
Dependent Manner ◽  
Rat Livers

Propofol, an intravenous anesthetic agent, is widely used for inducing and maintaining anesthesia during surgical procedures and for sedating intensive care unit patients. In the clinic, rapid elimination is one of the major advantages of propofol. Meanwhile, the biotransformation and drug interactions of propofol in rat livers are still little known. In this study, we evaluated the ring-oxidative metabolism of propofol in phenobarbital-treated rat livers and possible drug interactions. Administration of phenobarbital to male Wistar rats significantly increased levels of hepatic cytochrome P450 (CYP) 2B1/2 and microsomal pentoxyresorufinO-dealkylase (PROD) activity. Analyses by high-performance liquid chromatography and liquid chromatography mass spectroscopy revealed that propofol was metabolized by phenobarbital-treated rat liver microsomes into 4-hydroxypropofol. In comparison, PROD activity and 4-hydroxy-propofol production from propofol metabolism were suppressed by orphenodrine, an inhibitor of CYP2B1/2, and a polyclonal antibody against rat CYP2B1/2 protein. Furthermore, exposure of rats to propofol did not affect the basal or phenobarbital-enhanced levels of hepatic CYP2B1/2 protein. Meanwhile, propofol decreased the dealkylation of pentoxyresorufin by phenobarbital-treated rat liver microsomes in a concentration-dependent manner. Taken together, this study shows that rat hepatic CYP2B1/2 plays a critical role in the ring-oxidative metabolism of propofol into 4-hydroxypropofol, and this anesthetic agent can inhibit CYP2B1/2 activity without affecting protein synthesis.

Stimulation of Peroxidation in Rat Liver Microsomes by (Copper, Zinc)-Metallothioneins

1987 ◽  
Vol 4 (1) ◽  
pp. 15-20 ◽  
Author(s):  
John R. Arthur ◽  
Ian Bremner ◽  
Philip C. Morrice ◽  
Colin F. Mills
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
Rat Liver Microsomes ◽  
Copper Zinc ◽  
Stimulation Of
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