Question

Which of the following is increased in clinically normal cat during glucagon stimulation test?
A. Glycogenolysis
B. Gluconeogenesis
C. Glycolysis
D. Glycogenesis
Choose the correct answer from the options given below:

• A. B and C only
• B. A and B only
• C. C and D only
• D. B and D only

Hint:

The glucagon stimulation test is used clinically to assess hepatic glycogen reserves and insulin secretary capacity, as glucagon stimulates both hepatic glucose release and pancreatic insulin secretion.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Glucagon is a counter-regulatory peptide hormone secreted by the \(\alpha\)-cells of the pancreatic islets.
Its primary physiological role is to increase blood glucose concentration during hypoglycemia or metabolic demand.

Step 2: Detailed Explanation:
When glucagon binds to its G-protein-coupled receptors on hepatocytes, it activates adenylyl cyclase, raising intracellular cAMP levels and activating Protein Kinase A (PKA).
This signaling cascade stimulates metabolic pathways that release glucose into the bloodstream:
Glycogenolysis (A): Glucagon activates glycogen phosphorylase, promoting the rapid breakdown of stored liver glycogen into glucose-1-phosphate, which is then converted to free glucose.
Gluconeogenesis (B): Glucagon upregulates rate-limiting gluconeogenic enzymes (such as PEPCK and fructose-1,6-bisphosphatase), stimulating the synthesis of glucose from non-carbohydrate precursors like amino acids, lactate, and glycerol.
Conversely, glucagon inhibits glycolysis (C) and glycogenesis (D) to prevent futile cycling of glucose.
Thus, during a glucagon stimulation test, both glycogenolysis and gluconeogenesis are increased to elevate blood glucose levels.

Step 3: Final Answer:
The metabolic processes increased during a glucagon stimulation test are glycogenolysis and gluconeogenesis (A and B only).