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.

Effect of 2 inhibitors of oxidative phosphorylation on urea excretion in rats.

The effects of phloretin and carbonyl-cyanide-m-chlorophenylhydrazone (CCCP), both inhibitors of oxidative phosphorylation, on renal urea excretion in Wistar rats were investigated. Phloretin and CCCP infusions did not influence plasma urea concentration (P(urea)), compared with controls (0.15 M NaCl and Tris solution in 0.

Micropuncture study of the kidney in sheep: effects of iodoacetate on renal urea handling.

1. The effects of intrarenal infusion of iodoacetate, an inhibitor of anaerobic glycolysis, on urea transport in kidney of sheep was studied by micropuncture free-flow technique. 2.

Effect of dietary energy intake on tubular reabsorption of urea in sheep.

The aim of the experiment was to determine the effect of dietary energy intake on renal urea excretion in sheep with different nitrogen intakes. The control sheep, with a high nitrogen and energy intake, were given a daily feed dose of 21.18 g N and 15.

Creatinine and inulin clearance at the different nitrogen and energy intake in sheep.

1. Renal creatinine and inulin clearances were compared between sheep fed (a) high nitrogen and high energy diet; (b) low nitrogen and high energy diet and (c) low nitrogen and low energy diet. 2.

[The effect of water depletion on renal excretion of urea and electrolytes in sheep].

Experiments were conducted with the sheep of Merino breed given water only at a rate corresponding to 0.5% of their live weight for three days. The animals were given feed ad libitum and during the control measurements water was also available to them ad lib.

[Renal retention of urea in sheep].

The urea-retaining ability of kidneys of ruminants and returning it back to the blood circulation are important features of the mechanism of nitrogen conservation in the organism. Applying the model of a low-nitrogen diet to sheep we found out the low fractional excretion of urea (FE urea) as a result of increased urea transport capacity in renal tubules. The decrease in the amount of excreted urea by 85% was also accompanied by a reduced glomerular filtration rate (GFR).

Simple fluorometric ultramicroassay for urea in tubular fluid of the kidney.

Sensitive fluorometric method for the determination of picomole amount of urea in tubular fluid of the kidney is presented. It is a modification and simplification of the macromethod by McCleskey (6) for the urea determination in blood. Assay is based on the reaction of urea with diacetylmonoxime and sulphuric acid in boiling water within 20 minutes.

[Renal excretion of urea in the Merino and Steppe fat-tailed breeds of sheep after a short period of fasting].

Urea excretion was studied in an experiment with two sheep breeds (steppe fat-tailed and merino) on the second day of fasting when the urea concentration in blood increases in fasting animals. The control group in the two breeds was given free-choice feed and water while fasting sheep were given ad libitum only water. Diuresis in both breeds was steady during the experiment.

The renal response of sheep to a low dietary nitrogen intake.

Renal functions were tested in sheep fed on a low nitrogen diet (LN sheep), with a daily N intake of 4.7 g (gross energy 17.76 .

[Amino acid production in the isolated and perfused rumen wall of sheep].

The metabolism of amino acids and urea in an isolated perfused wall of sheep rumen was studied by the method of organ perfusion, using 3 kinds of perfusate. In experiments with semisynthetic perfusate containing urea (SPurea) the levels of lysine, valine, glutamic acid and alanine increased at a simultaneous decrease of levels of leucine, arginine, aspartic acid, threonine and methionine. In perfusions with the semisynthetic medium without urea (SP) the levels of lysine, valine, phenylalanine, isoleucine, glutamic acid, glycine and alanine increased, the level of threonine dropped.

[Renal excretion of urea and electrolytes in sheep after extracellular fluid expansion with an isotonic solution of sodium chloride].

Sheep of the Merino breed, given 10.11 g nitrogen daily (after Czechoslovak Standard CSN 46 7007) were studied for the effect of the expansion of the extracellular fluid (ECF) by an infusion of an isotonic solution of NaCl (at a rate of 5% of live weight), as exerted on the renal excretion of urea and on the sodium and potassium electrolytes. The high natriuresis, induced by the expansion of ECF, resulted in a statistically significant increase in the clearance of urea, free water, and solutions, and in higher diuresis.

[The effect of the antidiuretic hormone on the renal excretion of urea and electrolytes in fed and fasting sheep].

The effects of the antidiuretic hormone (ADH) on the renal excretion of urea and electrolytes were studied in sheep, subjected to water stress, before and after 36-hour fasting. The intravenous administration of synthetic lysine-vasopressin (L-VP) at the dose of 100 microgram per kg induced only a temporary, statistically insignificant, drop of the urinary urea outputs by the fed as well as fasting sheep. L-VP did not influence the excretion of sodium and potassium electrolytes either.

[Absorption of amino acids from the perfused ovine rumen].

The experiments with extracoroporeal perfusion of sheep rumen were performed [Leng et al., 1977]. Bovine plasma, diluted in a 1:1ratio with an isotonic solution of sodium chloride, was used for four perfusions, and autologous blood was used for two perfusions in the course of 150 minutes.

[Biological titration of antidiuretic activity of ovine plasma].

We studied a relationship of the antidiuretic hormone to the level of urea in the ovine blood. An antidiuretic activity of the ovine blood plasma before and after 36-hour fasting was determined by biological titration on 22-day-old rats. Optimum control doses were calculated as follows: 1.

[The passage of nitrogenous compounds through the wall of perfused sheep rumen (author's transl)].

Experiments were performed by the method of the extracorporeal perfusion of sheep rumen lasting 150 minutes. After 60 minutes of perfusion, 20 g of enzymatic casein hydrolyzate were applied to the rumen. Ammonia, urea, and total nitrogen were determined in the samples of perfusate, and ammonia and pH were determined in the rumen content.

[Extracorporeal perfusion of the sheep rumen].

We constructed a modified perfusion apparatus and elaborated a method of extracorporal perfusion of the rumen of sheep. As perfusates we used the bovine plasma diluted in a ratio of 1:1 of an isotonic sodium chloride (NaCl) solution and the whole autologous blood. Transaminases GOT and GPT, ammonia and pH were determined in the perfusate.