Mechanisms of disease

3. Targets for action of medicines

3.2. Transporter molecules

Other important targets include ‘transporter’ molecules, which serve either as channels or pumps. See Figure 5. These protein molecules also sit on the cell surface. They control the movement of salts (ions), metabolites, nutrients and medicines across the cell membrane. Ions like ‘calcium’ (Ca++) may also assist secretion, as above.

Transporters are also very important for the ‘absorption’ process in the gut - this is how nutrients from your food get into your blood. Again they control the movement of molecules from the body’s external surface to the inner compartments. They are crucial for the body’s homeostasis as they help to increase or decrease the concentration of metabolites and ions in the body. In the case of disease, it is possible to treat specific transporters through medicines that inhibit (decrease) or promote (increase) these processes, to restore homeostasis.

Since cell membranes do not allow water soluble substances to pass, transporters serve as ‘gates’ for what enters and leaves the cell. They therefore have an influence on the activity of the cell. An example of medicines that act on transporter molecules are ‘diuretics’. They control the excretion of salts (ions) via pumps in the kidney cells - this helps the body to remove excess salts and water through the urine.