A 50-year-old man with a remote history of alcohol dependence is evaluated in the clinic for chronic diarrhea and weight loss. The patient has had bloating with daily loose stools for the past 2 years. His stool is described as greasy and malodorous. Pancreatic insufficiency is suspected despite normal abdominal imaging. The patient undergoes a test in which bicarbonate concentration is measured from duodenal aspirates as hormone A is infused intravenously. The data is plotted in the graph below. Hormone A is most likely produced by which of the following cell types?

Question

A 50-year-old man with a remote history of alcohol dependence is evaluated in the clinic for chronic diarrhea and weight loss.  The patient has had bloating with daily loose stools for the past 2 years.  His stool is described as greasy and malodorous.  Pancreatic insufficiency is suspected despite normal abdominal imaging.  The patient undergoes a test in which bicarbonate concentration is measured from duodenal aspirates as hormone A is infused intravenously.  The data is plotted in the graph below.  Hormone A is most likely produced by which of the following cell types?

Quizplus · Accepted Answer

11ec160b_3cc3_aa98_9249_d9ca57944b1f_MD0001_00 Secretin is a hormone produced by intestinal S cells that increases bicarbonate secretion from the pancreas. Secretin stimulates the exocrine pancreatic ductal cells to release a high volume of bicarbonate-rich and chloride-poor fluid into the small bowel. The release of gastric acid into the duodenum is the most potent stimulus for secretin release, which begins as the duodenal pH drops below 5 and rises dramatically as the pH drops below 3. The sodium bicarbonate in the pancreatic secretions neutralizes the hydrochloric acid from the gastric contents in a reaction that produces sodium chloride and carbonic acid. Secretin has little to no effect on the secretion of enzymes from pancreatic acinar cells, which is instead under the control of cholecystokinin. (Choice B) Gastrin is the major hormone secreted by G cells of the gastric antrum. Gastrin increases parietal cell acid production and therefore increases the amount of acid delivered from the stomach to the duodenum. (Choices C and D) The endocrine pancreas is composed of glucagon-producing alpha cells, insulin-producing beta cells, and somatostatin-producing D cells. Insulin and glucagon help regulate blood glucose levels and metabolic homeostasis. Somatostatin inhibits the secretion of insulin, glucagon, gastrin, and most other gastrointestinal hormones. (Choice E) The liver parenchyma is not a significant source of circulating hormones that affect pancreatic exocrine function. (Choice F) Renal peritubular cells are responsible for producing erythropoietin, a hormone that stimulates red blood cell production in the bone marrow. Educational objective: Secretin is produced by S cells in the duodenal mucosa in response to stimulation by intraluminal acidity. Secretin stimulates the release of bicarbonate-rich secretions from the exocrine pancreas, which is the major source of acid-neutralizing bicarbonate entering the duodenum. __________ References: Secretin, 100 years later. (http://www.ncbi.nlm.nih.gov/pubmed/14673718) Neurohormonal control of exocrine pancreas. (http://www.ncbi.nlm.nih.gov/pubmed/17031194)

A 50-Year-Old Man with a Remote History of Alcohol Dependence