| مستخلص: |
The liver performs a wide range of physiologically important metabolic functions including the synthesis and secretion of albumin, fibrinogen, and other plasma proteins, the synthesis of cholesterol and bile acids, and the metabolism of drugs, steroids, and amino acids. In addition, the liver has a central role in energy metabolism as the major store of glycogen and the site of gluconeogenesis and synthesis of fatty acids and triglycerides. The liver is, therefore, a vital organ; however, it is sometimes difficult to study specific liver functions in vivo owing to interfering influences from other organs, e.g., the kidney, gut, and lungs, which metabolize drugs and the muscle involvement in glucose homeostasis. A number of in vitro preparations such as tissue homogenates or subcellular fractions are available to study tissue-specific functions, although experiments in intact cells, with cell membrane and cellular organelles are postulated to reflect the in vivo situation more closely. Hepatocytes represent 60-65% of the number of cells in the liver but occupy some 80% of the liver volume because of their large volume (1). Nonparenchymal cells such as Kuppfer cells, lipocytes, and endothelial cells (6%) make up the remaining tissue. Intercellular spaces account for approx 14% of the liver volume (1). Isolated human hepatocytes have been used extensively for a variety of techniques investigating cellular metabolism (2,3) and the induction (4-9), metabolism (10-14), and toxicology of xenobiotics (15,16). [ABSTRACT FROM AUTHOR] |
