scholarly journals Metabolism of urea in sheep

1967 ◽  
Vol 21 (2) ◽  
pp. 353-371 ◽  
Author(s):  
M. R. Cocimano ◽  
R. A. Leng
Keyword(s):  
Flow Rate ◽  
Crude Protein ◽  
Excretion Rate ◽  
Urine Flow ◽  
The Body ◽  
Urea Concentration ◽  
Urine Flow Rate ◽  
Entry Rate ◽  
Plasma Urea ◽  
Plasma Urea Concentration

1. The entry rates of urea into the urea pool of the body fluids have been measured in sheep given rations varying in crude protein percentage from 3.5 to 27.3.2. Results obtained with a single injection and with continuous infusions of [14C]urea were essentially the same.3. The difference between the entry rate and the rate of excretion of urea in the urine was taken to indicate the quantity of urea degraded in the alimentary tract.4. Plasma concentrations and urea entry rates were significantly and linearly related.5. The relationship between excretion rate and plasma urea concentration was best described by a cubic equation.6. Degradation of urea in sheep was found to be extensive in all the animals studied; as the protein intake increased, the quantity of urea degraded also increased but the percentage of urea entering the body pool that was degraded was decreased. Animals given a ration containing 3.5% crude protein degraded 76–92% of the urea entering the body pool.7. A rectilinear relationship was found between pool size and plasma urea concentration. The urea space in animals given low-protein rations was significantly less than in animals on high-protein rations.8. The effects of starvation for 2, 4 and 6 days on urea metabolism in sheep were investi-gated. In a11 the sheep starved for 2 days there was a significant increase in urea pool size, but the entry rate was markedly depressed indicating a retention of urea in the body pool on starvation.9. A significant amount of nitrogen was found to go through the system: rumen ammonia → portal blood ammonia→blood urea→rumen ammonia.10.Urea excretion rate, urea clearance by the kidney, urine flow rate and the ratio of the concentration of urea in urine to that in plasma (urea U:P ratio) were also examined.11. There were significant correlations between urine flow rate and urea excretion and between plasma urea concentration and urine flow rate.

scholarly journals Determination of nitrogen requirement for microbial growth from the effect of urea supplementation of a low N diet on abomasal N flow and N recycling in wethers and lambs

1976 ◽  
Vol 36 (3) ◽  
pp. 353-368 ◽  
Author(s):  
Sarah A. Allen ◽  
E. L. Miller
Keyword(s):  
Crude Protein ◽  
The Body ◽  
Urea Concentration ◽  
Metabolizable Energy ◽  
Entry Rate ◽  
Simple Diffusion ◽  
Plasma Urea ◽  
Urea Excretion ◽  
Plasma Urea Concentration ◽  
Microbial N

1. Plasma urea entry rate, urinary urea excretion and, by difference, urea recycling in the body, together with the flow of non-ammonia N through the abomasum and digestion of dry matter (dm) before the abomasum were determined in both wethers and lambs receiving cereal-starch diets supplemented with urea to give 60–120 g crude protein (N × 6.25)/kgdm.2. Lambs excreted less urea in urine than wethers given the same diet.3. Relationships between plasma urea entry rate or urine urea excretion rate and plasma urea concentration were different for lambs compared to wethers suggesting greater conser vation of body N by renal control in lambs.4. Recycling of urea was not related to plasma urea concentration in wethers but was related exponentially in lambs, suggesting recycling is controlled rather than the result of simple diffusion from the blood to the gastro-intestinal tract.5. Abomasal non-ammonia-N flow was similar for wethers and lambs and increased linearly with urea supplementation.6.dmdigestion prior to the abomasum was not significantly altered, although there was a tendency for decreased digestion of the basal diet given to lambs.7. Maximum microbial N flow to the abomasum was estimated as 30 g N/kg organic matter (OM) fermented in the rumen.8. This work and the literature reviewed suggested maximum net microbial production can be obtained when the diet supplies an amount of fermentable N equal to the microbial N output. It is calculated the diet should supply approximately 26 g fermentable N/kg digestible OM or 1.8 g fermentable N/MJ metabolizable energy. This corresponds to a fermentable crude protein supply varying from 65 to 130 g/kg DM as digestible OM content increases from 400 to 800 g/kg DM.

Factors affecting the urinary excretion of urea nitrogen in cattle. I. Sodium chloride and water loads

1970 ◽  
Vol 21 (1) ◽  
pp. 131 ◽  
Author(s):  
RF Thornton
Keyword(s):  
Sodium Chloride ◽  
Flow Rate ◽  
Free Water ◽  
Urine Flow ◽  
Urea Concentration ◽  
Urine Flow Rate ◽  
Urea Nitrogen ◽  
Plasma Urea ◽  
Urea Excretion ◽  
Plasma Urea Concentration

Urea metabolism in cattle was studied under conditions of different nitrogen, sodium chloride, and water intakes. Urea supplementation increased the concentrations of ammonia and trichloroacetic acid-insoluble nitrogen in ventral rumen fluid, raised the plasma urea concentration, and increased the excretion of faecal nitrogen and urinary urea and non-urea nitrogen. Sodium chloride loading increased the free water intake and urine flow rate, and the added sodium was quantitatively recovered in the urine. Plasma urea concentration was linearly related to urinary urea excretion but the slope of this relationship was influenced by the urine flow rate. Urea clearance and the fraction of filtered urea excreted were both related to the urine flow rate and to the urine-concentrating ability of the kidney, but not to the urinary urea output. During low nitrogen intakes, urinary urea excretion was influenced more by urine flow than by solute load.

UREA DEGRADATION IN THE CAMEL

1976 ◽  
Vol 56 (3) ◽  
pp. 595-601 ◽  
Author(s):  
B. EMMANUEL ◽  
B. R. HOWARD ◽  
M. EMADY
Keyword(s):  
Crude Protein ◽  
Urea Concentration ◽  
Pool Size ◽  
Entry Rate ◽  
Plasma Urea ◽  
Dietary Nitrogen ◽  
Urea Metabolism ◽  
Plasma Urea Concentration ◽  
Kinetics Of ◽  
General Plasma

Following a single injection of 14C-urea, the kinetics of urea metabolism have been studied in two female Arabian camels (Camelus dromedarius) fed roughage diets containing 6.1 (diet A), 9.6 (diet B), and 13.6% (diet C) crude protein. In general, plasma urea concentration, urea pool size, urea entry rate and urinary urea excretion rate increased as the dietary nitrogen intake increased. The mean extents of urea degradation were approximately 86, 74 and 47% for diets A, B, and C, respectively, as calculated from the ratio of urea degradation rate to urea entry rate, or from the fraction of 14C-urea recovered in the urine. The following parameters were linearly related: urea entry rate and urea pool size, urea pool size and plasma urea concentration, percentage urea degraded and urea entry rate, and percentage urea degraded and crude protein intake.

Renal Function in Unanaesthetized River Lampreys (Lampetra FluviatilisL.): Effects of Anaesthesia, Temperature and Environmental Salinity

1983 ◽  
Vol 105 (1) ◽  
pp. 351-362 ◽  
Author(s):  
A. J. MCVICAR ◽  
J. C. RANKIN
Keyword(s):  
Renal Function ◽  
Flow Rate ◽  
Ventilation Rate ◽  
Urine Flow ◽  
The Body ◽  
Urine Flow Rate ◽  
Flow Rates ◽  
Gill Ventilation ◽  
Daily Excretion ◽  
The Mean

1. Improved estimates of urine flow rates of lampreys in various salinities were obtained by the collection of urine for periods of up to 48 h from minimally-stressed, unanaesthetized fish, following catheterization of the urinogenital papilla. 2. The mean urine flow rate of freshwater lampreys was 200.7 ±14.3 ml kg−1 day−1. 3. Urine flow in freshwater lampreys was correlated with spontaneous changes in gill ventilation rate. MS222 anaesthesia reduced both ventilation and urine flow rates, but pronounced effects were only observed at concentrations greater than those needed to induce light anaesthesia (50–55 mg 1−1). Urine flow rate in unanaesthetized fish was extremely sensitive to rapid (6°Ch−1) changes in temperature and Q10 (6–16°C) was approximately 5. 4. Urine flow rate decreased rapidly as the osmotic difference between the body fluids and environment approached zero, and the rate of flow in 30% seawater lampreys was only 7.6% that of freshwater fish. 5. There was no evidence for an effect of environmental calcium concentration on branchial osmotic permeability. 6. Extensive tubular reabsorption of ions occurred in freshwater lampreys. The total daily excretion rate of sodium ions generally decreased in salinities hyperosmotic to the plasma, indicating enhanced reabsorption, but secretion of magnesium and sulphate ions was greatly increased. Urine osmolarity was significantly increased in lampreys in hyperosmotic salinities. 7. Present data compare favourably with data obtained previously from anaesthetized animals, indicating that renal function in lampreys is not significantly impaired by light MS222 anaesthesia.

Factors affecting the urinary excretion of urea nitrogen in cattle. II. The plasma urea nitrogen concentration

1970 ◽  
Vol 21 (1) ◽  
pp. 145 ◽  
Author(s):  
RF Thornton
Keyword(s):  
Nitrogen Concentration ◽  
Urine Flow ◽  
Urea Concentration ◽  
Urea Clearance ◽  
Urea Nitrogen ◽  
Plasma Urea ◽  
Factors Affecting ◽  
Urea Excretion ◽  
Plasma Urea Concentration ◽  
Filtered Load

The relationships between the plasma urea concentration and clearance variables associated with urinary urea excretion were investigated in urea-supplemented cattle. The plasma urea concentration was related to the urinary urea output, and thus to the urea clearance and the fraction of filtered urea excreted. It is suggested that the urine flow rate was influenced by urinary urea excretion, which in turn was influenced by the plasma urea concentration and therefore by the filtered load of urea. The probable influence of the recycling of urea to the rumen on the excretion of urinary urea is discussed.

Urea excretion in ruminants. II. Studies in sheep whose rumen contents were replaced with physiological saline

1970 ◽  
Vol 21 (2) ◽  
pp. 337 ◽  
Author(s):  
RF Thornton
Keyword(s):  
Maximum Concentration ◽  
Close Association ◽  
Physiological Saline ◽  
Urine Flow ◽  
Urea Concentration ◽  
Nitrogen Accumulation ◽  
Plasma Urea ◽  
Urea Excretion ◽  
Plasma Urea Concentration

Urea was infused intravenously into sheep whose rumen contents were removed and replaced with physiological saline. Despite large differences in plasma urea concentration the rate of nitrogen accumulation in the rumen, as urea plus ammonia, was similar at 6-7 mmoles/hr. The maximum concentration of nitrogen, as urea plus ammonia, was not influenced by plasma urea concentrations higher than 15-17 mg N/100 ml. Urinary urea excretion was positively related to plasma urea concentration but within any level of plasma urea concentration there was a close association between urine flow and urinary urea excretion.

Effect of Posterior Hypothalamic Lesions on Renal Function in the Rat

1971 ◽  
Vol 49 (11) ◽  
pp. 941-950 ◽  
Author(s):  
Alena Novakova ◽  
J. A. F. Stevenson
Keyword(s):  
Renal Function ◽  
Creatinine Clearance ◽  
Flow Rate ◽  
Posterior Hypothalamus ◽  
Urine Flow ◽  
The Body ◽  
Urine Flow Rate ◽  
Hypothalamic Lesions ◽  
Arterial Blood ◽  
Electrolytic Lesions

Female Wistar rats were infused with an isotonic solution (110 mM NaCl + 25 mM NaHCO3) containing 5 mU of Pitressin per milliliter, at a nonexpanding rate of 0.016 ml/min. Per-corten (1.25 mg i.m.) was given 1 h before the experiment. Urine flow rate, sodium and potassium excretion, and creatinine clearance were measured over 20-min periods. After the control values were obtained, bilateral electrolytic lesions were made in the posterior hypothalamus or the lateral hypothalamic area. Another group of rats was sham operated, and in controls an equivalent current was passed through the body. Posterior hypothalamic lesions were immediately followed by significant increases in the urine flow rate, UNa, and UNaV. Creatinine clearance increased insignificantly. However, the significant decrease of the fractional sodium reabsorption indicated that the natriuresis was mainly of tubular origin. This diuresis and natriuresis were not associated with significant changes in the arterial blood pressure. Changes were still detectable 60 min after lesioning, but were returning to control levels. No changes in renal function followed lesions in the lateral hypothalamus, sham operation, or application of electric current. The role of the posterior hypothalamus in the renal excretion of sodium is discussed.

scholarly journals The effects of dietary sucrose and the concentrations of plasma urea and rumen ammonia on the degradation of urea in the gastrointestinal tract of cattle

1980 ◽  
Vol 43 (1) ◽  
pp. 125-140 ◽  
Author(s):  
P. M. Kennedy
Keyword(s):  
Gastrointestinal Tract ◽  
Medicago Sativa ◽  
Multiple Regression ◽  
Ammonia Concentration ◽  
Urea Concentration ◽  
Entry Rate ◽  
Plasma Urea ◽  
Plasma Urea Concentration ◽  
The Relationship ◽  
Microbial N

1. The rates of entry of urea into plasma, of urea degradation in the gastrointestinal tract, and the partition of that degradation between the rumen and post-ruminal tract were determined by use of [14C]urea and NaH14CO3 in Hereford steers receiving hay diets with or without sucrose. The concentrations of plasma urea and rumen ammonia were varied by infusions of urea into the rumen or abomasum.2. For all diets, plasma urea concentration was related to urea entry rate, to degradation of urea in the whole gastrointestinal tract, and to its degradation in the post-ruminal tract, but the relationship with its degradation in the rumen was poor.3. Degradation of urea in the rumen was related in a multiple regression in a curvilinear manner in three groups of diets (pasture-hay alone, pasture-hay–lucerne (Medicago sativa) mixtures, diets with sucrose), and negatively to rumen ammonia concentration for pasture-hay diets, and diets with sucrose.4. Ruminal clearance of urea (rate of urea degradation per plasma urea concentration) was negatively related to the rumen ammonia concentration for steers given diets with sucrose, of pasture-hay with or without urea infusions. Provision of sucrose in the diet significantly increased clearance.5. Enhanced urea degradation in the rumen associated with dietary sucrose supplements accounted for 0.4 of additional microbial N synthesis in the rumen.6. The partition of transfer of urea to the rumen via saliva and through the rumen wall is discussed.

Atrial natriuretic peptide, right atrial pressure, and sodium excretion rate in the rat

1987 ◽  
Vol 253 (5) ◽  
pp. F969-F975 ◽  
Author(s):  
T. A. Fried ◽  
M. A. Ayon ◽  
G. McDonald ◽  
A. Lau ◽  
T. Inagami ◽  
...  
Keyword(s):  
Atrial Natriuretic Peptide ◽  
Natriuretic Peptide ◽  
Flow Rate ◽  
Sodium Excretion ◽  
Volume Expansion ◽  
Excretion Rate ◽  
Balloon Catheter ◽  
Urine Flow ◽  
Urine Flow Rate ◽  
Right Atrial

This study examined the relationship between right atrial pressure (RAP), urine flow rate, sodium excretion rate, and plasma atrial natriuretic peptide (ANP) levels after an acute Ringer expansion. Two groups of rats had their RAP monitored and balloon catheters placed in their thoracic inferior venae cavae. In one group the balloon remained deflated, and in the second group the balloon was inflated during the volume expansion in an attempt to prevent the rise in RAP. The peak RAP was 7.3 +/- 0.8 mmHg when the balloon remained deflated and 3.5 +/- 0.6 mmHg in the group with the balloon catheter inflated (P less than 0.005). The corresponding peak ANP levels were 682 +/- 140 and 223 +/- 40 pg/ml. There was a significant correlation between the peak RAP and ANP levels (r = 0.754; P less than 0.05). The inflation of the balloon catheter significantly decreased the urine flow rate and the urine sodium excretion rate. A final group of animals had 200 microliters of rabbit serum containing antibody to ANP infused before the volume expansion. The antibody-treated animals had significantly lower urine flow and sodium excretion rates than nonantibody-treated control rats. We conclude that ANP is one of the factors which allows the rat to excrete an acute Ringer expansion.

scholarly journals Whole body Kt/V from dialysate urea measurements during hemodialysis.

1998 ◽  
Vol 9 (11) ◽  
pp. 2118-2123
Author(s):  
J Sternby
Keyword(s):  
Removal Rate ◽  
Plasma Concentrations ◽  
The Body ◽  
Urea Concentration ◽  
Whole Body ◽  
Water Volume ◽  
Dialysis Dose ◽  
Plasma Urea ◽  
Urea Distribution Volume ◽  
Plasma Urea Concentration

A new method for the calculation of dialysis dose from continuous measurements of dialysate urea concentrations has been developed. It is based on urea mass in the patient instead of plasma concentrations, and results in a measure of dialysis dose that has been named whole body Kt/V. The measured urea mass removal rate and the slope of the dialysate urea concentration curve are the key parameters needed for the calculations. No assumptions have to be made about urea distribution in the body (single or double pool, etc.). Blood sampling is not needed. This simplifies the logistics and eliminates the problems with rebound and timing in taking samples. The total urea mass present in the body before treatment is also obtained. It can be used directly, or in relation to body weight or water volume, as a measure of the level of urea in the body. This may serve as an alternative to pretreatment plasma concentration. If a pretreatment plasma urea concentration is available, the urea distribution volume can be calculated, which may be of separate clinical interest.

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