Storage of lipids

STORAGE OF LIPID MESSENGERS IN NEURAL MEMBRANE PHOSPHOLIPIDS 576... 

The general rules that should therefore be observed include the use of a blanket of nitrogen whenever possible and evaporation of solvents at the lowest feasible temperatures, which must not exceed 50°C. The addition of an antioxidant such as butylated hydroxytoluene (2,6-di-/-butyl-4-methylphenol) to the extraction solvents (0.1 g 1 ) might be necessary to prevent deterioration of unsaturated lipids but it is essential for storage of lipid extracts at about 0.1% of the weight of lipid. Inactivation of lipolytic enzymes may usually be achieved by addition of an alcohol such as methanol or, in some cases, isopropanol. The latter is recommended for some more stable enzymes sometimes found in plant tissues. Alternatively the plant may be briefly immersed in boiling water. 

Ethanol-related high levels of NADH+H and acetyl-CoA in the liver lead to increased synthesis of neutral fats and cholesterol. However, since the export of these in the form of VLDLs (see p. 278) is reduced due to alcohol, storage of lipids occurs (fatty liver). This increase in the fat content of the liver (from less than 5% to more than 50% of the dry weight) is initially reversible. However, in chronic alcoholism the hepatocytes are increasingly replaced by connective tissue. When liver cirrhosis occurs, the damage to the liver finally reaches an irreversible stage, characterized by progressive loss of liver functions. 

Studies conducted by different authors on the release of chemical substances from medical devices, mainly those used for infusing solutions, show that these are potential sources of contamination for pharmaceutical formulations. One of the most studied is diethylhexyl phthalate, the same plasticizer found in PVC infusion bags to give flexibility. The same concerns about the use of PVC bags for the storage of lipids or lipophilic formulations are valid for tubing. 

Zhou, S., Ackman, R.G., and Morrison, C. 1995. Storage of lipids in the myosepta of Atlantic Salmon (Salmo salar). Fish Physiol. Biochem. 14 171-178. 

Answer Unlike water-soluble compounds, lipid-soluble compounds are not readily mobilized— that is, they do not readily pass into aqueous solution. The body s lipids provide a reservoir for storage of lipid-soluble vitamins. Water-soluble vitamins cannot be stored and are rapidly removed from the blood by the kidneys. 

Insulin stimulates uptake of glucose and amino acids by cells, glycogen and protein synthesis, and storage of lipids. It inhibits glycogenolysis, gluconeogenesis, breakdovm of stored triglycerides, and ketogenesis. 

At first glance affected subjects do not present with remarkable features. Closer examination reveals striking discoloration and enlargement of the tonsils in addition, spleen, lymph nodes and liver may be enlarged. Organomegaly is caused by storage of lipids, particularly of cholesterol esters. Changes compatible with lipid deposition have also been described in the cornea and in the intestinal mucosa. 

Autoxidation is always a concern for storage of lipid extracts. They should not be stored in a dry state, but dissolved in a small volume of a relatively nonpolar (aprotic) solvent. The lipid samples should be stored at -20 C at least in a glass (never plastic) container. Air should be excluded from the container by flushing with a stream of nitrogen. Antioxidants should be used for prolonged storage. 

Atherosclerotic plaque is a complex lesion which is a result of an inflammatory and reparative process. The atheroma plaque contains extracellular deposits of calcium salts, blood components, cholesterol crystals, and acid mucopolysaccharides. The initial changes, however, seem to occur at the cellular level, often accompanied by an abnormal intracellular storage of lipids, particularly cholesterol esters, fatty acids, and lipoprotein complexes. The rupture of the plaque can generate thrombosis, reductions in the vessel lumen and consequently in the cardiac perfusion, and acute or chronic consequences. 

Special care was taken to minimise exposure to light. Samples were tak to dryness and resu ended in prc an-2-ol/hexane/water/methanQl (56/38.5/3.3/2.2 v/v) for HPLC s aration. All solutions used for the extraction and storage of lipids contained 0.01 % butylated hydroxytcluene and 0.2 % o(-tocopherol as antioxidants. Galactolipids were separated and analysed a modification of the gradient HPLC method of Heemskerk et al. (7). 

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