Lipoprotein plasma, major

Distribution - The mean volume of distribution is 12 L/kg. Sirolimus is extensively bound (approximately 92%) to human plasma proteins. The binding of sirolimus was shown mainly to be associated with serum albumin (97%), - -acid glycoprotein, and lipoproteins. The majority of sirolimus is... 

ANIMALS TRANSPORT LIPIDS in an aqueous environment at concentrations up to one million times their solubility in water. They accomplish this task by surrounding water-insoluble lipids with amphipathic lipids and proteins to form plasma lipoproteins. A major part of lipid transport is to supply energy for muscle contraction and to deliver lipids to adipose tissue for storage. Disorders in lipoprotein metabolism are a major risk factor for premature coronary heart disease throughout the world. These disorders arise from dysfunction in apolipoproteins, particular enzymes, and lipid transfer proteins, and also secondary to disorders in carbohydrate metabolism. 

Certain enzymes, proenzymes, and their substrates are present at all times in the circulation of normal individuals and perform a physiologic function in the blood. Examples of these functional plasma enzymes include lipoprotein Upase, pseudocholinesterase, and the proenzymes of blood coagulation and blood clot dissolution (Chapters 9 and 51). The majority of these enzymes are synthesized in and secreted by the liver. 

Cholesterol (Figure 14-17) is widely distributed in all cells of the body but particularly in nervous tissue. It is a major constituent of the plasma membrane and of plasma lipoproteins. It is often found as cholesteryl ester, where the hydroxyl group on position 3 is esteri-fied with a long-chain fatty acid. It occurs in animals but not in plants. 

Four Major Groups of Plasma Lipoproteins Have Been Identified... 

Vitamin E is the Major Lipid-Soluble Antioxidant in Cell Membranes Plasma Lipoproteins... 

The intima of the arterial wall contains hyaluronic acid and chondroitin sulfate, dermatan sulfate, and heparan sulfate proteoglycans. Of these proteoglycans, dermatan sulfate binds plasma low-density lipoproteins. In addition, dermatan sulfate appears to be the major GAG synthesized by arterial smooth muscle cells. Because it is these cells that profiferate in atherosclerotic lesions in arteries, dermatan sulfate may play an important role in development of the atherosclerotic plaque. 

The concentration of total protein in human plasma is approximately 7.0-7.5 g/dL and comprises the major part of the solids of the plasma. The proteins of the plasma are actually a complex mixture that includes not only simple proteins but also conjugated proteins such as glycoproteins and various types of lipoproteins. Thousands of antibodies are present in human plasma, though the amount of any one antibody is usually quite low under normal circumstances. The relative dimensions and molecular masses of some of the most important plasma proteins are shown in Figure 50-1. 

Tandia B, et al. Lipid mixing between lipoplexes and plasma lipoproteins is a major barrier for intravenous transfection mediated by cationic lipids. J Biol Chem 2005 280 12255. 

Research on plasma lipoproteins has entered a highly productive period during which major advances have been made from both the conceptual and technological standpoints. The information gained on lipoprotein apoproteins has particular relevance, especially in terms of pri-... 

Distribution - In vitro orlistat was greater than 99% bound to plasma proteins (lipoproteins and albumin were major binding proteins). Orlistat minimally partitioned into erythrocytes. 

Plasma lipoproteins can be divided into six major classes (see Fig. 5.2.1). Four of these classes derive from the liver and are present in the plasma of fasted subjects very-low-density lipoproteins (VLDL), intermediate-density lipoproteins (IDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL). The other two classes of lipoproteins derive from the intestine and are found in the plasma of nor-molipidemic individuals only after a fatty meal (postprandially) chylomicrons and chylomicron remnants. 

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