Question

The enterohepatic circulation of bile acids A. necessitates participation of secondary active \(\mathrm{Na}^{+}\) -bile acid cotransport. B. results in the reabsorption of only the primary bile acids. C. maintains the body pool of bile acids at \(20-30 \mathrm{g}\) D. maintains serum levels of bile acids at a constant value. E. uses the same transport mechanism to secrete bile acids from the liver to bile as from the enterocyte to the blood.

Short answer

A. The enterohepatic circulation necessitates participation of secondary active Na+-bile acid cotransport. B. The enterohepatic circulation results in the reabsorption of only the primary bile acids. C. The enterohepatic circulation maintains the body pool of bile acids at 20-30 g. D. The enterohepatic circulation maintains serum levels of bile acids at a constant value. E. The enterohepatic circulation uses the same transport mechanism to secrete bile acids from the liver to bile as from the enterocyte to the blood. Answer: The correct statements regarding the enterohepatic circulation of bile acids are A, C, and D.

Step-by-step solution

Statement A#

The enterohepatic circulation necessitates participation of secondary active \(\mathrm{Na}^{+}\)-bile acid cotransport. In the ileum, bile acids are reabsorbed through an active transport mechanism called apical sodium-dependent bile acid transporter (ASBT), which uses sodium gradients to facilitate bile acid absorption. So, this statement is true.

Statement B#

The enterohepatic circulation results in the reabsorption of only the primary bile acids. This statement is incorrect because both primary and secondary bile acids are absorbed by the enterohepatic circulation.

Statement C#

The enterohepatic circulation maintains the body pool of bile acids at \(20-30 \mathrm{g}\). This statement is true. The enterohepatic circulation tightly regulates the amount of bile acids in the body, maintaining an optimal concentration to ensure proper digestion and absorption of dietary lipids.

Statement D#

The enterohepatic circulation maintains serum levels of bile acids at a constant value. This statement is true. The enterohepatic circulation is vital for keeping serum levels of bile acids constant by regulating their absorption and excretion.

Statement E#

The enterohepatic circulation uses the same transport mechanism to secrete bile acids from the liver to bile as from the enterocyte to the blood. This statement is incorrect. The liver uses the bile salt export pump (BSEP) to secrete bile acids into canalicular bile, whereas the ileal enterocytes utilize the organic solute transporter-alpha/beta (OST-alpha/beta) to export bile acids from the cell into the portal venous blood. In conclusion, statements A, C, and D are correct, while statements B and E are incorrect.