USMLE Forums banner
1 - 5 of 5 Posts

·
Registered
Joined
·
557 Posts
Discussion Starter · #1 ·
A healthy 24 y/o man participates in a clinical study. serum-levels of proinsulin derived C-peptide are measured after various provocative stimuli. Administration of which of the following will most likely produce the lowest levels of circulating C-peptide?
A. CCK
B. Clonidine
C. Glucagon
D. Terbutalline
E. Theophylline

Try to explain your answer (but still take a guess even if you don't want to explain :)
 

·
Registered
Joined
·
88 Posts
The answer is clonidine(B).
Clonidine is an alpha -2 agonist, by so doing, it mimics the feedback inhibition of norepinephrine release form nerve endings., hence inhibiting insulin release from the Beta islet cell which have alpha-2 receptors.
alpha-methyl dopa is another drug in this category.

On the other hand, drugs that activate beta-2 receptors increase insulin release.
 

·
Registered
Joined
·
487 Posts
The answer is clonidine(B).
Clonidine is an alpha -2 agonist, by so doing, it mimics the feedback inhibition of norepinephrine release form nerve endings., hence inhibiting insulin release from the Beta islet cell which have alpha-2 receptors.
alpha-methyl dopa is another drug in this category.

On the other hand, drugs that activate beta-2 receptors increase insulin release.
That's right,
Also caused by non selective beta blockers.
 

·
Registered
Joined
·
557 Posts
Discussion Starter · #5 ·
The answer is clonidine(B).
Clonidine is an alpha -2 agonist, by so doing, it mimics the feedback inhibition of norepinephrine release form nerve endings., hence inhibiting insulin release from the Beta islet cell which have alpha-2 receptors.
alpha-methyl dopa is another drug in this category.

On the other hand, drugs that activate beta-2 receptors increase insulin release.
Yes, you're correct! Alpha-2 receptor agonists such as clonidine directly inhibit pancreatic insulin secretion and therefore also decrease secretion of proinsulin derived c-peptide.

Note that although endogenous glucagon suppresses insulin secretion, exogenous glucagon does the opposite. injected glucagon raises blood sugar (which is why it's effective in emergency treatment of hypoglycemia), and therefore stimulates insulin release.
 
1 - 5 of 5 Posts
Top