Question
Which of the following hormones acts via an intracellular receptor in skeletal muscle cells?
| A. |
Insulin |
| B. |
Corticosteroid |
| C. |
Epinephrine |
| D. |
Glucagon |
Show Answer
|
Correct Answer » B Explanation |
 |
- Hormones exert their effects by binding either:
- Intracellular (cytoplasmic or nuclear) receptors, or
- Cell surface (membrane) receptors.
- Lipid-soluble hormones diffuse across the plasma membrane and bind intracellular receptors.
- Water-soluble hormones cannot cross the lipid bilayer and therefore act through membrane receptors.
- Corticosteroids are steroid hormones derived from cholesterol.
- They are lipid-soluble and readily diffuse through the cell membrane.
- They bind to intracellular glucocorticoid or mineralocorticoid receptors located in the cytoplasm or nucleus.
- The hormone-receptor complex regulates gene transcription, resulting in protein synthesis.
- Therefore, muscle cells contain intracellular receptors for corticosteroids.
Why Other Options are Incorrect
A. Insulin
- Insulin is a peptide hormone.
- It binds to a cell surface receptor tyrosine kinase (RTK).
- It does not have intracellular receptors.
C. Epinephrine (Adrenaline)
- Epinephrine is a catecholamine.
- It binds to α- and β-adrenergic G-protein-coupled receptors (GPCRs) on the cell membrane.
D. Glucagon
- Glucagon is a peptide hormone.
- It acts through a G-protein-coupled receptor (GPCR) on the plasma membrane.
- Skeletal muscle also lacks glucagon receptors; glucagon primarily acts on the liver.
