Physiological effects of pH changes on colloid osmotic pressures

Abstract

Our purpose was to explore the effects of variations in pH, particularly in the physiological range, on the colloid osmotic pressure (COP) of the body's fluids. Theoretically, changing pH would alter the electrical charge density on plasma proteins and the interstitial ground substance, thereby altering plasma and interstitial protein osmotic pressure as well as interstitial fluid pressure. We found that the COP of human plasma, human albumin, bovine albumin, and Wharton's jelly from human umbilical cords increased linearly as pH increased over the range of 6.0-8.0. COP of plasma and the albumins all displayed essentially the same sensitivity to pH. At equal concentrations, hyaluronate in umbilical cords was approximately 16 times more sensitive to pH than was plasma. Dextran 70 displayed no COP dependency on pH. For plasma, the albumins, and hyaluronate the pH dependence of COP on pH also decreased linearly with concentration (C in g/dl). For plasma and the albumins over the physiological range of pH, COP = COPpH 7.4 [1.00 + 0.01C (pH -7.40)] at 37 degrees C. The data suggest that, relative to the normal net transcapillary pressure gradient, physiological variations in pH affect plasma COP as well as interstitial fluid pressure and thus may play a significant role in regulating the body's fluid distribution.

Swelling and pressure-volume relationships in the dermis measured by osmotic-stress technique

“…Results with these two polymers of very different physicochemical structure were similar. Table 2 confirms that the volume changes observed in the dermal explants depend on the colloidosmotic gradients between the bulk fluid and dermis rather than other effects; for example, changes in the osmotic pressure of the polymer solution with pH and temperature (26,32) or in the viscosity with concentration.…”

Thoracic Duct Lymph Flow in Fetal Sheep with Increased Venous Pressure from Electrically Induced Tachycardia

“…The calculated effect of this pH change on col loid osmotic pressure is a decrease of 0.02 mm Hg, whereas the colloid osmotic pressure that we measured with pacing was decreased by 1.1 mm Hg [14], Therefore, the decrease in colloid osmotic pressure is attrib utable to the small decrease in plasma protein concentration rather than to the decrease in pH. The changes in plasma protein concentra tion and in colloid osmotic pressure were not significant in this study.…”

Endotoxin increases both protein and fluid microvascular permeability in cat skeletal muscle

“…Using the proposed relation between colloid osmotic pressure and pH (30), the reflection coefficient ratio is overestimated by Ͻ1% in these experiments.…”

“…The decrease in pH after endotoxin (Table 1) may have decreased the colloid osmotic pressure (30), resulting in an overestimation of the reflection coefficient ratio in the endotoxin group. Using the proposed relation between colloid osmotic pressure and pH (30), the reflection coefficient ratio is overestimated by Ͻ1% in these experiments.…”