Plasma water

Plasma water, also referred to as bulk water, is the aqueous component of blood plasma that serves as the primary solvent for nutrients, gases, and metabolic waste products (Guyton and Hall Textbook of Medical Physiology). Although it is not a biological macromolecule like a receptor or enzyme, it is functionally targeted by osmotic agents to manipulate fluid distribution within the body (StatPearls: Osmotic Diuretics). Drugs such as mannitol and glycerol exert their effects by increasing the osmolality of the plasma water, creating an osmotic gradient that draws fluid from the intracellular or interstitial compartments into the vascular space (PubChem: Mannitol). This physiological manipulation is clinically utilized to reduce intracranial pressure in cerebral edema or to promote diuresis in acute kidney injury (NIH: Fluid and Electrolyte Balance). Consequently, while not a target in the proteomic sense, the physical properties of plasma water are central to the pharmacodynamics of volume-expanding and osmotic therapies.

Other names

Bulk waterExtracellular waterPlasma solventAqueous phase of plasmaSerum water

Osmotic modulation; increasing the osmotic pressure of the plasma or tubular fluid to induce the movement of water across biological membranes via an osmotic gradient (StatPearls: Osmotic Diuretics).