Solvent drag, also known as bulk transport, is a phenomenon primarily in renal physiology, but it also occurs in gastrointestinal physiology. It is when solutes in the ultrafiltrate are transported back from the renal tubule by the flow of water rather than specifically by ion pumps or other membrane transport proteins.
It generally occurs in the paracellular, rather than transcellular, pathway across the tubular cells.
It is seen e.g. in the passive transport in renal sodium reabsorption, renal chloride reabsorption as well as renal urea handling.
- ^ Walter F., PhD. Boron. Medical Physiology: A Cellular And Molecular Approach. Elsevier/Saunders. ISBN 1-4160-2328-3. Page 791