This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Pharmacology
Mechanism of action of the sulfonylureas is 
Select and explain. 
A. K+ ATP channel blocker, B. Na ATP channel blocker, C. Cl ATP channel blocker, D. Ca ATP channel blocker.
A: K+ ATP channel blocker
Answer: A: K+ ATP channel blocker 
Explanation: Ans. is 'a' i.e., K ATP channel blocker * Sulfonylurease provoke a brisk release of insulin from pancreas. They act on the so called "Sulfonylurea receptors" (SUR1) on pancreatic b-cell membrane - cause depolarization by reducing conductance of ATP sensitive K+ channels. This enhances influx of Ca+2 - degranulation. They do not cause hypoglycemia in pancreatectomized animals and type 1 diabetes (Presence of at least 30% of functional b-cells in essential for their action). A minor action reducing glucagon secretion by increasing insulin and somatostatin release has been demonstrated.