Solvent drag, also known as bulk transport, refers to
solute
In chemistry, a solution is defined by IUPAC as "A liquid or solid phase containing more than one substance, when for convenience one (or more) substance, which is called the solvent, is treated differently from the other substances, which are ...
s in the
ultrafiltrate that are transported back from the
renal tubule by the flow of water rather than specifically by
ion pumps or other
membrane transport protein
A membrane transport protein is a membrane protein involved in the movement of ions, small molecules, and macromolecules, such as another protein, across a biological membrane. Transport proteins are integral membrane proteins, integral transmembr ...
s.
[ Page 791] This is a phenomenon primarily in
renal physiology
Renal physiology (Latin language, Latin ''renes'', "kidneys") is the study of the physiology of the kidney. This encompasses all functions of the kidney, including maintenance of acid-base balance; regulation of fluid balance; regulation of sodiu ...
, but it also occurs in gastrointestinal physiology.
It generally occurs in the
paracellular, rather than
transcellular, pathway between 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.
References
{{renal physiology
Renal physiology
de:Solvent Drag