Studies on the transcapillary escape rate of albumin and capillary permeability in rhesus monkeys infected with Plasmodium knowlesi

The transcapillary escape rate and plasma clearance rate of albumin were studied in five rhesus monkeys infected with Plasmodium knowlesi in comparison with six control monkeys by using 125I-HSA as a tracer. The plasma disappearance curve of the radioactivity was followed during the first 60 minutes after injection of this labelled protein. Plasma volume was found to be significantly higher while plasma albumin concentration was significantly lower, which resulted in the non-significantly increased intravascular albumin mass in the infected group. The mean values of the transcapillary escape rate, plasma clearance rate and the outflux of albumin from the intravascular to the extravascular compartments in the infected group were found to be significantly higher than those of the control group. This indicated that there was an increased leakage of plasma albumin from the circulation into the extravascular space in rhesus monkeys infected with P. knowlesi. As both capillary effective pore area per unit path length available for restricted diffusion and the specific permeability coefficient of plasma albumin were found to be significantly increased in the infected group, therefore the increased leakage of albumin was probably due to the increased surface of capillary membrane.