BIOM20002 Lecture Notes - Lecture 34: Circulatory System, Morphine, Probenecid
Document Summary
Blue is bowman"s capsule space: is proximal convoluted tubules. About 180 litres per day (about 40 blood volume) Physical separation on the basis of size and charge. Larger or negatively charged species get through less easily. Proteins remain in blood - protein-bound drug is not filtered (e. g. thyroxine) about 15% 20% of the delivered plasma is filtered. Much mt to make atp for active transport. Active pumping of solutes into the filtrate by: Organic cation transporters (octs): e. g. atropine, morphine, adrenaline, creatinine. Organic anion transporters (oats): bile salts, aspirin, penicillin, probenecid (prolongs half-life of penicillin by competing for oat) Similar processes in the liver pump drugs into bile. Competition between substrates can occur (e. g. probenecid and penicillin) Active processes: drugs can be actively transported by transporters designed for other species, e. g. glucose uptake in proximal tubules. Passive diffusion: mostly lipid-soluble molecules (often ph dependent). Lipid soluble drugs can diffuse through cell membranes back into blood.
