Heterogeneity of the intrahepatic biliary epithelium

Table 1 Terminology and relationship between human and rat intrahepatic bile ducts

Terminology for human bile ducts(diameter inμm)	Terminology for rat bile ducts(diameter inμm)
(Large bile ducts)
Hepatic ducts (> 800)
Segmental ducts (400-800)
Area ducts (300-400)
(Small bile ducts)
Septal bile ducts (100-300)
Interlobular bile ducts (15-100)	Large bile ducts (> 15)
Bile ductules (cholangioles) (< 15)	Small bile ducts (< 15)

These data have been obtained from studies[8,12,13] aimed to define the morphological characteristics of the biliary epithelium of rats, and humans. Reproduced with permission from Ref 2.

Table 2 Expression and function of proteins and surface transporters in small and large ducts from rats and human

Markers	Small ducts	Large ducts	Function	References
γ-glutamyl transpeptidase	Not expressed	Interlobular large rat bile ducts	Glutathione metabolism	[81]
Alkaline phosphatase	Not expressed	Interlobular large rat bile ducts	Inhibition of secretin choleresis	[81]
Leucine amino peptidase	Not expressed	Interlobular large rat bile ducts	Undefined	[81]
Cytochrome P4502E1	Not expressed	Expressed by large rat and human ducts	Dehalogenation of CCl4	[50,81,104,105]
Lipase, α-amylase and trypsin	Human septal ducts	Large human ducts, and peribiliary glands	Biliary tree development	[79,80]
Bcl-2	Human small ductules	Not expressed	Anti-apoptotic protein	[109,143]
Secretin receptor	Not expressed	Expressed by large rat ducts	Stimulation of bicarbonate secretion	[12,13,48,54]
CFTR	Human but not rodent small ducts	Expressed by large rat ducts	Regulation of Cl--secretion	[54]
Cl-/HCO3- exchanger	Not expressed	Expressed by large rat and human ducts	Regulation of ductal bicarbonate secretion	[12,13,82]
Somatostatin receptor	Not expressed	Expressed by large rat ducts	Inhibition of secretin choleresis	[48]
D2 dopamine receptors	Unknown	Expressed by large rat ducts	Inhibition of secretin choleresis	[25]
α-1 adrenergic receptors	Expressed by small rat ducts	Expressed by large rat ducts	Stimulation of secretin choleresis	[65]
Endothelin receptors	Expressed by small rat ducts	Expressed by large rat ducts	Inhibition of secretin choleresis	[59]
Na+-dependent ABAT	Not expressed	Expressed by large rat ducts	Regulation of ductal secretion	[88]

Heterogeneous expression of proteins and membrane transporters that may play a role in the modulation of the heterogeneous properties of the intrahepatic biliary tree of rats and human. Modified with permission from Ref 73.