All of the following act through cell surface receptors except?
**Core Concept**
The question is testing the understanding of receptor-mediated drug action, specifically the distinction between cell surface and intracellular receptors. Cell surface receptors are transmembrane proteins that receive signals from extracellular ligands, whereas intracellular receptors are located within the cell and respond to ligands that can cross the plasma membrane.
**Why the Correct Answer is Right**
The correct answer is an intracellular receptor, which acts through a different mechanism. Intracellular receptors, such as steroid hormone receptors, are located within the cell and respond to ligands that can diffuse through the plasma membrane. Once activated, these receptors translocate to the nucleus, where they regulate gene expression.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it represents a cell surface receptor, which is the opposite of the correct answer. Cell surface receptors are responsible for receiving signals from extracellular ligands and triggering a response within the cell.
**Option B:** This option is incorrect because it also represents a cell surface receptor. Like Option A, it is the opposite of the correct answer and would not act through an intracellular receptor.
**Option C:** This option is incorrect because it represents another type of cell surface receptor. While it may have some intracellular signaling pathways, it ultimately acts through a cell surface receptor mechanism.
**Clinical Pearl / High-Yield Fact**
Intracellular receptors, such as steroid hormone receptors, are often referred to as "nuclear receptors" because they regulate gene expression in the nucleus. This is in contrast to cell surface receptors, which can regulate gene expression through various signaling pathways.
**Correct Answer: D.**