Renal response of sheep fed a low protein diet to intraportal infusion of arginine and glycine.

The renal effects of infusions of arginine and glycine into the portal vein were studied in the anaesthetized sheep with a reduced glomerular filtration rate (GFR) after 6 weeks of low dietary protein intake. Arginine significantly elevated urine flow (V), whole kidney GFR and the amount of urea excreted (UureaV) concomitantly with plasma urea level (P(urea)) without changes in fractional urea excretion (FEurea). Sheep infused with glycine showed significantly increased urinary flow only. Free-flow micropuncture of the late proximal tubule revealed that both the fluid flow and single nephron GFR were increased by arginine without any significant changes in tubular fluid to plasma inulin ratio. There was no effect of glycine on the micropuncture parameters of the sheep kidney. These results suggest that the synthesis of urea from arginine in the liver and its subsequent delivery to the kidney may be involved in the regulation of dietary induced changes of the glomerular filtration rate in sheep.