The effects of progressive nutritional hypoproteinaemia of the extracellular-fluid phase and plasma colloid osmotic pressure in rats

Abstract

In rats fed for 7 days on a vegetable protein-deficient diet (I) the water content of plasma and of tissues, the plasma protein concn. and the plasma colloid osmotic pressure remained unchanged. In spite of this the extracellular-fluid phase of skeletal muscles and of liver had significantly increased, showing that there was tissue edema with normal plasma protein concn. and normal colloid osmotic pressure. In rats fed for 14 days on I there was a significant increase in the water content of the plasma, the muscles and the liver, with a decrease in the plasma protein concn. and a slight but significant decrease in the colloid osmotic pressure of plasma. The extracellular-fluid phase of the muscles was significantly greater than that of rats fed for 7 days on I. Comparing data obtained for rats fed for 42 days on I with those for animals fed for 70 days on a diet equally low in protein but yielding an adequate supply of calories (II) it was shown that the extracellular-fluid phases of muscle and liver were markedly increased, and the concn. of proteins in plasma significantly decreased in both series. The mean colloid osmotic pressure of normal rat plasma amounted at 37[degree] to 19.6 + 0.12 cm. water; that of rats fed on I for 7 days was 19.2 [plus or minus] 0.19 cm.; I for 14 days, 16.3 [plus or minus] 0.51 cm.; I for 42 days, 10.2 [plus or minus] 0.87 cm.; and II for 70 days, 10.6+ 0.71 cm. The colloid osmotic pressure of plasma of the 3 latter groups was correlated with the albumin/globulin (A/G) ratio of plasma, but not with the N concn. of the plasma samples. In the cases of a few rats fed for 42 days on I and for 70 days on II, the colloid osmotic pressure of plasma samples was lower than that expected from either the A/G ratio or the plasma nitrogen concn. No correlation was found between the increase of the extracellular-fluid phase of tissues and the decrease of the colloid osmotic pressure of the plasma.