| Hepatocytes make up 60-80% of the cytoplasmic mass of the liver. These cells are involved in protein synthesis, protein storage and transformation of carbohydrates,
synthesis of cholesterol, bile
salts and phospholipids, and detoxification, modification and excretion
of exogenous and endogenous substances. The hepatocyte also initiates the formation and secretion of bile.
Protein synthesis
The hepatocyte is the only cell in the body that manufactures albumin, fibrinogen, and the prothrombin group of clotting factors. It is the main site for the synthesis of lipoproteins, ceruloplasmin,
transferrin, and glycoproteins. Hepatocytes manufactures their own structural proteins and intracellular enzymes.
Synthesis of proteins is undertaken by the rough endoplasmic reticulum (RER), and both the rough and smooth endoplasmic reticulum (SER) are involved in
secretion of the proteins formed. The endoplasmic
reticulum (ER) is involved in conjugation of proteins to lipid and carbohydrate moieties synthesized by, or modified within,
the hepatocytes.
Carbohydrate metabolism
The liver forms fatty acids from carbohydrates and synthesizes triglycerides from fatty acids and glycerol. Hepatocytes also synthesize
apoproteins with which they then assemble and export lipoproteins (VLDL, HDL).
Lipid metabolism
The liver receives many lipids from the systemic circulation and metabolizes chylomicron remnants. It also synthesizes cholesterol from acetate and then further synthesizes bile salts. The liver is the sole site of formation of bile salts.
Detoxification
Hepatocytes have the ability to metabolize, detoxify, and inactivate exogenous compounds such as drugs and insecticides, and endogenous compounds such as steroids. The drainage of the intestinal
venous blood into the liver requires efficient detoxification of miscellaneous absorbed substances to maintain homeostasis and protect the body against ingested toxins. One of the detoxifying
functions of hepatocytes is to modify ammonia to urea for excretion.
Storage
Hepatocytes are important depots for vitamin B12 and iron.
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