Renal plasma flow in rhesus monkeys infected with Plasmodium knowlesi.

: Renal plasma flow was studied in six rhesus monkeys before and during infection with Plasmodium knowlesi using 125I-sodium orthoiodohippurate (125I-OIH) as a tracer. The mean renal plasma flow and the rate constant from the intravascular compartment to the kidneys were significantly reduced in the infected monkeys. As both intravascular and extravascular compartments were slightly but not significantly elevated, which resulted in the prolonged mean transit time of 125I-OIH in monkeys infected with P. knowlesi. The parasitemia showed a reverse relationship with the renal plasma flow and a direct relationship with the mean transit time. These findings indicated that the renal plasma flow in the infected monkeys was depressed in proportion to the number of P. knowlesi parasites. The mechanism of reduced renal plasma flow was probably due to renal vasoconstriction.