Plasma osmotic pressure

**Plasma osmotic pressure** refers to the component of total osmotic pressure exerted by solutes within the blood plasma across capillary walls. It is primarily determined by the concentration of large proteins in the plasma—mainly albumin—and to a lesser extent by electrolytes[1][2]. This force opposes hydrostatic (blood) pressure and acts to draw water from interstitial spaces back into capillaries during capillary exchange[1]. The term "plasma oncotic" or "colloidal osmotic" pressure specifically describes the portion due to proteins that cannot cross semipermeable membranes[1][2]. The maintenance of appropriate plasma osmotic/oncotic pressures is essential for normal distribution of body fluids between vascular and interstitial compartments. Disruption can lead to clinical conditions such as edema when low protein levels reduce reabsorption forces. **Plasma osmotic/oncotic pressures are not molecules or receptors**, but rather emergent physical properties resulting from dissolved substances in solution. Therefore, they are *not* considered therapeutic targets like enzymes, transporters, ion channels, or receptors. In summary: > Plasma osmotic (or colloidal) pressure is **not itself a molecule/receptor**, but rather an important physiological parameter reflecting the ability of solutes—primarily proteins—to retain water within the vascular compartment[1][2][3]. If you require information about specific molecules involved in generating this property (such as "serum albumin"), those would be valid molecular targets.

Other names

Blood colloidal osmotic pressureOncotic pressurePlasma oncotic pressure