Protein loss and capillary protein permeability in dependent regions upon quiet standing

Abstract

Seven healthy males were exposed to quiet standing (15 min) after supine rest. Alterations in the total mass of plasma proteins were analysed from changes in plasma volume (PV; determination of control PV and subsequently of induced per cent PV changes using Hb/Hct) and protein concentration as revealed in arterial blood collected after standing. This approach adopted the concept that valid data on overall circulatory haemoconcentrations prevailing on standing can only be reached when blood is sampled on resumption of the recumbent posture, whereas conventional sampling from the standing subject provides erroneous information. The PV reduction on standing averaged 649 +/- 65 mL (16.9 +/- 1.0%). There were very similar net decreases in plasma (serum) total protein (7.6 +/- 0.8 g) and albumin (7.8 +/- 0.9 g). These findings permitted the following main conclusions of physiological and methodological pertinence: (1) Quiet standing leads to a clear-cut net decrease in the plasma protein content predominantly confined to albumin, in all probability via convection secondary to PV loss by filtration in dependent regions. (2) It is suggested that the albumin loss reflects a quite high capillary macromolecular permeability in the dependent limbs on standing preferentially confined to skin/subcutaneous tissues. (3) The albumin loss implies that plasma concentration changes of neither albumin nor of total protein can be used to describe the PV loss on standing. However, concentration changes of the plasma globulin fraction as a whole, expressed by the difference (total protein-albumin), seem to reflect PV alterations approximately.

Postural Pseudoanemia: Posture-Dependent Change in Hematocrit

“…These various studies have shown that PV may shift from 10% up to 18% [11][12][13][14] in response to a person changing from a supine to an upright posture. Plasma volume shifts that may contribute to aberrant Hct values have been observed by many researchers using various techniques, including Evans blue dye, carbon monoxide dilution, and the mechanical oscillator technique.…”

Extracellular fluid and its proteins: dehydration, shock, and recovery

“…PV and glomerular filtration rate decrease [29]. In a recent study [30] as much as 20% of PV was sequestered in ESF within 15 min. There was a similar decrease in plasma albumin content (approximately 20%), but no decrease in larger proteins.…”

Gravity, the hydrostatic indifference concept and the cardiovascular system

“…Changing from supine to upright leads to an increase of both systemic haematocrit and plasma protein concentration (Thompson et al 1928;Hagan et al 1978;HinghoferSzalkay et al 1995;Bjerkhoel et al 1995). This means that below the location of hydrostatic indifference, where capillary pressures rise after assumption of an erect position, the extent of filtration out of the microvascular bed exceeds the inward fluid movement that, at the same time, occurs in capillaries above the hydrostatic indifference level.…”