Download 2008b(12): Detail the protective and regulatory roles of the liver

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Transcript
Endocrine, Metabolism & Exercise
2008b(12): Detail the protective and regulatory roles of the liver.
General: the liver is the largest gland in the body and has multiple functions
involved in many essential processes in the body. It is the interface between the
gut and the body and therefore has a role in protection from organisms and
toxins and regulation of nutrient levels.
Protective:
- involved in removal of bacteria, endotoxins and protein denaturation
- these actions are primarily undertaken by Kupffer Cells located in the
hepatic sinusoids
- the actions of these macrophages are an example of innate immunity
- Kupffer Cell activitation initiates a chain of events:
o phagocytosis → complement activation → recruitment of other
cells
- can function as a blood reservoir:
o 450mL in the liver at resting state
o can ↑ to 1500mL in fluid overload
o ↓intravascular volume → able to mobilize 350mL
- production of acute phase proteins
- drug biotransformation:
o phase I: oxidation (enzyme systems eg CYP450) → unmask
conjugation sites
o phase II: conjugation to ↑solubility for excretion
Regulatory:
- primarily acts as a glucostat
- metabolic roles are hormonally influenced
o catabolic hormones: glucagons, cortisol, adrenaline
o anabolic hormones: insulin, GH
- anabolic functions
o CHO: glycogenesis
 ↑glucose trapping (hepatocytes) 2° ↑glucokinase activity
o fats:
 fatty acid formation
• once maximal glycogen stores → glucose
metabolized to pyruvate → AcetylCoA → fatty acid
 cholesterol/phospholipids formation
o proteins:
 lipoproteins synthesis
- catabolic functions:
o CHO: glycogenolysis, gluconeogenesis (via acetyl CoA
formation from fatty acid breakdown) → maintain BSL
o fats: ↑lipolysis
 ketone body formation
 bile acid formation (for fat absorption)
o proteins:
 ammonium formation (via glutathione synthesis for
transport to PCT in kidney)
By Michael Wirth
Endocrine, Metabolism & Exercise
urea: by product amino acid metabolism →
↑concentrating ability of kidney
regulating production of albumin to control plasma oncotic pressure
production of bile in regulating fat and fat soluble vitamin absorption
bilirubin metabolism
hormone inactivation
production of both coagulant and anti-coagulant proteins
involved in the storage of:
o amino acids
o iron (as ferritin)
o glycogen
o lipid soluble vitamins (A, D, E, K)
o copper

-
By Michael Wirth