Micropuncture study on urea movements in the kidney cortical tubules of low protein fed sheep.

Micropuncture studies of late proximal, early and late distal cortical tubules were carried out on kidneys of normal (NP) and low (LP) protein fed sheep in order to investigate the participation of these segments in the urea sparing induced by protein restriction in the diet. A low protein diet induced significant reductions in the fractional (-54%) and total (-84%) urea excretion, revealing an enhanced capacity for urea conservation. Micropuncture data did not show any difference in the proximal tubule functions between both groups of sheep.

[The effect of a low-protein diet on the epithelium of nephron segments in sheep].

Changes in the epithelium thickness of proximal and distal convoluted tubule of cortex, thin descending limb of Henle loop from inner stripe of outer medulla, thick ascending limb from outer stripe of outer medulla and of collecting duct from inner medulla were investigated in young growing sheep fed a low protein diet (LP). Sheep on LP-diet were given a daily ration with 5.73 g of nitrogen and 6.

Urine concentrations in the spaces of the sheep renal pelvis.

Urine concentrations were measured in samples from the ureter, the pelvic cavity, close to the tip of the papilla, and from the most proximal part of the fornices of sheep kidneys. It was found that the concentration of urea, the osmolality, and the urine-to-plasma ratios of inulin, urea and the osmolality were higher in the ureter than in the pelvic cavity. The same parameters were found to be higher in the pelvic cavity than in the fornices except for the urea concentration which was unchanged.

Partition of nitrogenous substances in the urine of sheep on different dietary protein intakes.

The distribution of nitrogenous substances in urine was studied in sheep fed high (28.71 g N daily) and low (9.32 g N daily) protein diets for 6-8 weeks.

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.