Skip to 0 minutes and 14 seconds Factors affecting the transport of proteins include molecular size, membrane permeability, plasma macromolecule binding, tissue uptake, active transport, lymphatic transport, and vascular transport. And we are going to discuss each and every one of these in the following slides. Okay. So let’s look at how proteins are transported in our body system.
Skip to 0 minutes and 54 seconds The first I want to talk about is the transport by convection. Convection is the transport of a constituent or a biological molecule by bulk motion of the fluid. So convection is driven by hydrostatic pressure, that is the pressure between the influx point and the outflux point. And the transport rate is determined by flux J is equal to V times C, where V is the flow rate and C is the concentration of biologics. The other transport mechanism is diffusion. And this applies to small molecules and also oligopeptides, the small peptide. Let’s look at GI membrane as an example. Here you have the GI membrane. This is the mucosa site of the membrane and this is the serosa site of the membrane.
Skip to 2 minutes and 7 seconds The molecules diffuse from the mucosa site to the serosa site and is emptied from the serosa site into general circulation. And in this transport mechanism, the flux or the diffusion rate is dependent on the concentration gradient between, in this case, the serosa site of the concentration and the capillary site of the drug concentration. Let’s look at another transport by endocytosis and exocytosis. So in this slide, the bottom one is the endocytosis where the biologics molecules become engulfed in the endocytic vesicle. And then they are able to travel across the membrane. And on the other side of the membrane, is the exocytosis where the drug molecules actually bulge out or move away from the membrane.
Transport of Biologics in the Body
The delivery of drugs to a target site frequently involves distribution and transport across various biological barriers. Factors that influence the transport of biologics include molecular size, membrane permeability, macromolecule binding and tissue uptake. The degree and nature of the impediment to drug flux will be addressed. Diffusive and convective mechanisms of drug transport are detailed. Lymphatic, vascular, endocytic and exocytic pathways of drug transport are highlighted.
Two primary transport mechanisms are discussed, diffusion and convection; specific drug transporters will be presented only as a backdrop. Three transport pathways are discussed, of which vascular route is largely for small molecules and oligopeptides. Lymphatic system, endocytosis and exocytosis are primarily for large molecule biologics. Finally, the factors that influence biologics distribution and transport are summarized, including molecular size, membrane permeability, macromolecule binging and tissue uptake.