Pharmacology
Pharmacology
Core12: Membrane transport mechanisms
膜輸送機構
🚪 High-yield / 要点：Membrane transport = passive diffusion, carrier-mediated transport, endocytosis, exocytosis. Transporters are mainly ABC efflux pumps and SLC influx/efflux carriers.
Transport mechanisms / 膜輸送機構
| Mechanism | Subtype | Key point |
|---|---|---|
| Passive transport | Lipid diffusion | Non-ionized, lipid-soluble drugs pass easily |
| Passive transport | Aqueous diffusion | Small water-soluble molecules pass through aqueous pathways |
| Carrier-mediated transport | Facilitated diffusion | Uses transporter; no direct ATP use |
| Carrier-mediated transport | Active transport | Energy/gradient dependent; can move against gradient |
| Vesicular transport | Endocytosis / exocytosis | Important for large molecules and cellular uptake/release |
Transporter families / トランスポーター
| Family | Main function | Energy source | Examples / notes |
|---|---|---|---|
| ABC transporters | Mainly efflux | ATP-driven | MDR1 / P-glycoprotein; intestinal epithelium, BBB, testis, placenta |
| SLC transporters | Influx and some efflux | Ion-gradient driven | OAT, OCT; also neurotransmitter uptake transporters |
P-glycoprotein / P-gp
- MDR1 / P-glycoprotein pumps drugs out of cells.
- Important locations:
- Intestinal epithelial cells.
- Blood-brain barrier endothelial cells.
- Testis.
- Placenta.
- Inhibition of MDR1, e.g. grapefruit, ritonavir, can increase drug exposure → therapeutic or toxic.
Remember / 覚え方
- Non-ionized + lipid-soluble = crosses membranes well
- ABC = ATP + efflux
- SLC = solute carrier + gradient
- P-gp protects barriers but causes drug interactions