Alterations in capillary permeability in rhesus monkeys with Plasmodium knowlesi infection.

The transcapillary escape rate and capillary permeability to albumin were studied in 3 rhesus monkeys throughout the whole course of P. knowlesi infection. The transcapillary escape rates started to increase on the first week after infection and were significantly higher than the control values during infection. Plasma volume was found to be increased while plasma albumin concentration decreased which resulted in the increased intravascular mass, outflux and clearance of albumin from the intravascular to the extravascular compartments. Increased As/delta X and Ps during malarial infection indicated that the increased capillary permeability was due to increased capillary surface area and the increased endothelial permeability. As there was no relationship between increased plasma volume or intravascular mass of albumin and As/delta X or Ps, the increased capillary permeability in these infected monkeys could not be explained by the stretching pore phenomena. As these parameters show a close relationship to the parasitemia, therefore malarial parasites may play a role in causing increased capillary permeability.