RESUMO
Investigations were carried out on the influence of rat liver plasma membranes phospholipid composition on phospholipase C activity using PIP, PIP2, PC and PE as substrates. The membrane phospholipids were modified by incorporation of definite phospholipids with the aid of lipid transfer proteins or after partial delipidation with exogenous phospholipases A2 and C. The results indicated that sphingomyelin inhibited all phospholipase C activities. The incorporation of two different molecular species of phosphatidylcholine did not alter significantly the investigated phospholipase C activities, indicating that membrane fluidity was not essential in this case. Phosphatidylglycerol, phosphatidylserine, phosphatidylinositol and phosphatidylethanolamine served as specific activators of plasma membrane-bound phospholipase C when PIP, PIP2 and PC were used as substrates. However, these four phospholipids inhibited phospholipase C activity towards PE. The role of phosphoinositide-specific phospholipase C in the production of second messengers as well as the eventual biological significance of PC and PE as substrates for phospholipase C is discussed.
Assuntos
Fígado/enzimologia , Fosfolipídeos/metabolismo , Fosfolipases Tipo C/metabolismo , Animais , Membrana Celular/enzimologia , Hidrólise , Fígado/ultraestrutura , Masculino , Lipídeos de Membrana/metabolismo , Fosfatidilcolinas/metabolismo , Fosfatidiletanolaminas/metabolismo , Fosfatidilinositol 4,5-Difosfato , Fosfatos de Fosfatidilinositol/metabolismo , Fosfatidilinositóis/metabolismo , Ratos , Ratos WistarRESUMO
1. Treatment of rats with carbicron induced a reduction of the phospholipids in both microsomal and plasma membranes. 2. A decrease of the structural order parameter (SDPH) and an increase of the pyrene excimer-to-monomer fluorescence ratio (IE/IM) was also observed, indicating membrane fluidization. 3. The specific activity of membrane-bound phospholipase A2 and phospholipase C were decreased in both types of membranes, whereas acyl-CoA:lysophosphatidylcholine acyltransferase activity was augmented due to carbicron treatment.
Assuntos
Membrana Celular/efeitos dos fármacos , Fígado/ultraestrutura , Compostos Organofosforados/farmacologia , 1-Acilglicerofosfocolina O-Aciltransferase/metabolismo , Animais , Membrana Celular/fisiologia , Fenômenos Químicos , Físico-Química , Membranas Intracelulares/efeitos dos fármacos , Membranas Intracelulares/fisiologia , Fígado/efeitos dos fármacos , Masculino , Fluidez de Membrana , Microssomos Hepáticos/ultraestrutura , Fosfolipases A/metabolismo , Fosfolipases A2 , Fosfolipídeos/química , Fosfolipídeos/metabolismo , Ratos , Ratos Wistar , Fosfolipases Tipo C/metabolismoRESUMO
1. Intoxication of rats with carbicron (O-([2-butenoic acid)-N,N-dimethylamide-3-yl]-O,O-dimethylphosphate) induced a reduction of the total phospholipids and phosphatidylcholine in lung alveolar surfactant. 2. The lipid transfer protein activity was inhibited due to carbicron treatment. 3. No alterations were observed in phospholipase A2 activity in the alveolar surfactant of intoxicated animals. The structural order parameter (SDPH) of bilayer liposomes, prepared from surfactant phospholipids of carbicron-treated rats also remained unchanged.
Assuntos
Inseticidas/toxicidade , Compostos Organofosforados/toxicidade , Alvéolos Pulmonares/efeitos dos fármacos , Surfactantes Pulmonares/efeitos dos fármacos , Animais , Proteínas de Transporte/antagonistas & inibidores , Proteínas de Transporte/metabolismo , Polarização de Fluorescência , Masculino , Fosfolipases A/efeitos dos fármacos , Fosfolipases A/metabolismo , Fosfolipases A2 , Fosfolipídeos/metabolismo , Alvéolos Pulmonares/enzimologia , Alvéolos Pulmonares/metabolismo , Surfactantes Pulmonares/metabolismo , Ratos , Ratos WistarRESUMO
The influence of immobilization stress on the lipid composition of alveolar surfactant and lungs in rats immobilized for 12 and 24 hours, the effects of phospholipase A2, and lipid transfer activity in alveolar surfactant were investigated. The results indicate that alveolar surfactant phospholipids underwent more significant alterations compared to lung phospholipids. Furthermore, phospholipase A2 and lipid transfer activity were reduced in alveolar surfactant of immobilized rats. The reported data suggest that the lower lipid transfer activity might be responsible for the reduced phospholipids in the surfactant system.
