This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gall Bladder & Bile Ducts, Subject name: Surgery
Which of the following enzymes are elevated in cholestasis? 
Select and explain. 
A. Alkaline phosphatase, B. 5' nucleotidase, C. Gamma glutamyl transpeptidase, D. All the above
D: All the above
Answer: D: All the above 
Explanation: Ans. is 'd' i.e., All the above Enzymes in cholestasis* The activities of three enzymes-- alkaline phosphatase, 5'-nucleotidase, and y-glutamyl transpeptidase (GGT)--are usually elevated in cholestasis.* Alkaline phosphatase and 5'-nucleotidase are found in or near the bile canalicular membrane of hepatocytes, while GGT is located in the endoplasmic reticulum and in bile duct epithelial cells.* Reflecting its more diffuse localization in the liver, GGT elevation in serum is less specific for cholestasis than are elevations of alkaline phosphatase or 5'-nucleotidase.