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

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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Nitrogen metabolism and plasma urea concentrations in fleeceweight-selected and control Romney rams

Australian Journal of Agricultural Research ◽

10.1071/ar9870917 ◽

1987 ◽

Vol 38 (5) ◽

pp. 917 ◽

Cited By ~ 14

Author(s):

SN McCutcheon ◽

DDS Mackenzie ◽

HT Blair

Keyword(s):

Creatinine Clearance ◽

Clearance Rate ◽

Urine Output ◽

Plasma Concentrations ◽

Nitrogen Retention ◽

Urea Concentration ◽

Plasma Urea ◽

Plasma Urea Concentration ◽

And Control ◽

Daily Period

Nitrogen retention and plasma urea concentrations were examined in 2-year-old Romney rams from fleeceweight-selection and control lines. In four experimental periods rams were fed chaffed lucerne hay (110% of maintenance energy requirements) three times daily (Period I), twelve times daily (Period II), twice daily (Period IV), or were fasted (Period 111). Nitrogen balance was measured in Period I, while plasma concentrations, urinary excretions and clearances of urea and creatinine were examined in Periods II-IV. Water intake and urine output were measured in all periods. Plasma urea concentrations were also measured in the same rams at grazing. Differences between the lines in water intake, urine output, faecal and urinary nitrogen excretion and nitrogen retention were not significant. Control rams maintained significantly higher plasma concentrations of urea and creatinine than fleeceweight-selected rams but only under controlled feeding conditions (particularly twelve times daily feeding). Differences between the lines in plasma urea concentration could be accounted for by the (non-significantly) greater urinary urea excretion, and lower creatinine clearance rate, of control rams. Measurement of plasma urea concentration in sheep may provide a useful predictor of genetic merit for fleeceweight. However, it will be necessary to measure plasma urea concentration under controlled feeding conditions to accurately rank animals. Concurrent measurement of creatinine clearance rate and urinary urea excretion should also enhance the accuracy of prediction of genetic merit.

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Salinity Adaptation in the Salamander Batrachoseps

Journal of Experimental Biology ◽

10.1242/jeb.76.1.1 ◽

1978 ◽

Vol 76 (1) ◽

pp. 1-10

Author(s):

RONALD M. JONES ◽

STANLEY S. HILLMAN

Keyword(s):

Tap Water ◽

Plasma Concentrations ◽

Urea Concentration ◽

Short Term ◽

Osmotic Concentration ◽

Plasma Urea ◽

Sucrose Solutions ◽

Urine Production ◽

Plasma Urea Concentration

(1) Batrachoseps attenuatus and B. major were successfully acclimated to 600 m-osmol NaCl and 400 m-osmol sucrose solutions. (2) Accumulation of sodium and an increased rate of synthesis of urea provide substantial increases in plasma concentrations of these solutes. Sodium concentrations in excess of 230 mM and urea concentrations in excess of 200 mM indicate that these are the two major solutes (plus anions) responsible for elevation of osmotic concentration in Batrachoseps. (3) Batrachoseps exhibits a water balance response upon dehydration (greater than twofold increase in cutaneous uptake, 50% reduction in urine production). Urine production, estimated from bladder contents, was significantly reduced in salamanders acclimated to sucrose solutions compared to animals acclimated to tap water or saline of equivalent osmotic concentration. (4) Plasma urea concentration was equivalent to urine urea concentration when Batrachoseps was kept in tap water and during short term saline acclimation. After long term saline acclimation, urine urea concentration was one-fourth the plasma urea concentration.

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Pulsatile urea excretion in the toadfish (Opsanus beta) is due to a pulsatile excretion mechanism, not a pulsatile production mechanism

Journal of Experimental Biology ◽

10.1242/jeb.200.6.1039 ◽

1997 ◽

Vol 200 (6) ◽

pp. 1039-1046 ◽

Cited By ~ 5

Author(s):

C Wood ◽

T Hopkins ◽

P Walsh

Keyword(s):

Blood Plasma ◽

Great Majority ◽

Urea Concentration ◽

Whole Body ◽

Head Region ◽

Plasma Urea ◽

Water Compartments ◽

External Water ◽

Plasma Urea Concentration ◽

Natural Pulse

When subjected to a crowding/confinement protocol in the laboratory, toadfish become facultatively ureotelic, excreting approximately 90 % of their nitrogenous waste as urea-nitrogen (urea-N). The great majority of this excretion occurs via large, irregular pulses from the head region which occur on average once per day, with a duration of 3 h or less. Pulses measured chemically by the appearance of urea-N in the external water were identical to those measured by assaying [14C]urea appearance in the water from the blood plasma. Individual toadfish maintained plasma urea concentrations over widely differing ranges (660039 890 µmol-N l-1). However, independent of absolute levels, both [14C]urea and total urea were distributed at ratios close to unity between the blood plasma and the water compartments of liver and white muscle. At times of pulsatile excretion, plasma urea concentration fell sharply. These decreases, distributed throughout the tissues of the whole body, closely matched the sizes of the measured excretion pulses. Between pulses, plasma urea concentration increased steadily at a much slower rate; the rate of rise, when distributed throughout the tissues of the whole body, corresponded to the time-averaged excretion rate over the whole day. Infusion of a typical pulse amount of urea immediately after the end of a natural pulse event raised plasma urea concentration slightly above the pre-pulse level, but did not induce another pulse event. Plasma cortisol levels declined by approximately 60 % over the 4 h period prior to a natural pulse event and then rose quickly again once the pulse had occurred. These results indicate that urea pulses are due to activation of an excretion mechanism that rapidly clears urea from the blood plasma, thereby lowering stores throughout the whole body. Metabolic production of urea is continuous and is not responsible for pulsatile excretion. The pulse event is not triggered by a specific plasma urea threshold, but may involve the hypothalamointerrenal axis.

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Metabolism of urea in sheep

British Journal Of Nutrition ◽

10.1079/bjn19670037 ◽

1967 ◽

Vol 21 (2) ◽

pp. 353-371 ◽

Cited By ~ 113

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.

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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

British Journal Of Nutrition ◽

10.1079/bjn19760092 ◽

1976 ◽

Vol 36 (3) ◽

pp. 353-368 ◽

Cited By ~ 58

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.

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The effect of dietary protein restriction on the secretory dynamics of 1α-hydroxycorticosterone and urea in the dogfish, Scyliorhinus canicula: a possible role for 1α-hydroxycorticosterone in sodium retention

Journal of Endocrinology ◽

10.1677/joe.0.1380275 ◽

1993 ◽

Vol 138 (2) ◽

pp. 275-282 ◽

Cited By ~ 39

Author(s):

K. J. Armour ◽

L. B. O'Toole ◽

N. Hazon

Keyword(s):

Dietary Protein ◽

Sea Water ◽

Plasma Concentrations ◽

Protein Restriction ◽

Urea Concentration ◽

Rectal Gland ◽

Plasma Urea ◽

Dietary Protein Restriction ◽

Scyliorhinus Canicula ◽

Plasma Urea Concentration

ABSTRACT The putative osmoregulatory role of the unique elasmobranch corticosteroid, 1α-hydroxycorticosterone (1α-OH-B), was investigated using dietary protein restriction as a means of limiting urea biosynthetic ability. Groups of dogfish (Scyliorhinus canicula) were adapted to either a high or a low protein diet (HPD and LPD respectively) and the secretory dynamics of urea and 1α-OH-B were determined following acclimation to normal (100%), 130% and 50% sea water. In normal sea water, LPD fish showed significantly decreased blood production of urea compared with fish fed a HPD (P <0·05), and the plasma urea concentration required to maintain iso-osmolality was achieved only by a substantial decrease in urea clearance from the plasma. Unlike HPD fish, LPD fish in 130% sea water had no apparent ability to increase plasma urea concentration. An alternative strategy adopted by these animals was the retention of high plasma concentrations of Na+ and Cl−, which increased plasma osmolality and tended to decrease osmotic water loss. Concomitant with the increased ion concentrations, plasma 1α-OH-B concentration was also greatly elevated in LPD fish indicating that the steroid may be acting to minimize Na+ (and Cl−) excretion at osmoregulatory sites such as the rectal gland, kidney and gills. This and a previous study have also demonstrated that 1α-OH-B concentration is elevated in 50% sea water. Decreases in plasma Na+ concentration are tolerated down to 75% sea water, whereafter Na+ is preferentially retained and further decreases in osmolality are achieved by reductions in plasma urea concentration. Increased 1α-OH-B concentration in 50% sea water corresponds to Na+ retention and regulation around a lower set point. The results of this study are consistent with a mineralocorticoid role for 1α-OH-B in elasmobranchs, with 1α-OH-B acting preferentially to maintain plasma Na+ concentrations under certain osmotic conditions. Journal of Endocrinology (1993) 138, 275–282

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Genome-wide association for plasma urea concentration in sheep

Livestock Science ◽

10.1016/j.livsci.2021.104483 ◽

2021 ◽

Vol 248 ◽

pp. 104483

Author(s):

Taiana Cortez de Souza ◽

Tatiana Cortez de Souza ◽

Gregorí Alberto Rovadoscki ◽

Luiz Lehmann Coutinho ◽

Gerson Barreto Mourão ◽

...

Keyword(s):

Urea Concentration ◽

Genome Wide Association ◽

Plasma Urea ◽

Genome Wide ◽

Plasma Urea Concentration

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Urea Excretion in the Camel

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1957.188.3.477 ◽

1957 ◽

Vol 188 (3) ◽

pp. 477-484 ◽

Cited By ~ 81

Author(s):

Bodil Schmidt-Nielsen ◽

Knut Schmidt-Nielsen ◽

T. R. Houpt ◽

S. A. Jarnum

Keyword(s):

Glomerular Filtration Rate ◽

Glomerular Filtration ◽

Filtration Rate ◽

Urea Concentration ◽

Nitrogen Excretion ◽

Renal Tubules ◽

Urea Clearance ◽

Plasma Urea ◽

Urea Excretion ◽

Plasma Urea Concentration

The nitrogen excretion was studied in the one-humped camel, Camelus dromedarius. When a growing camel was maintained on a low N intake (dates and hay) the amount of N excreted in the form of urea, NH3 and creatinine decreased to 2–3 gm/day. This decrease was caused by a drop in urea excretion from 13 gm to 0.2–0.5 gm/day. Urea given intravenously during low N intake was not excreted but was retained. (The camel like other ruminants can utilize urea for microbial synthesis of protein.) The renal mechanism for urea excretion was investigated by measuring urea clearance and glomerular filtration rate during a period of 7 months. During normal N intake about 40% of the urea filtered in the glomeruli were excreted in the urine while during low N intake only 1–2% were excreted. The variations in urea clearance were independent of the plasma urea concentration and of glomerular filtration rate, but were related to N intake and rate of growth. No evidence of active tubular reabsorption of urea was found since the urine urea concentration at all times remained higher than the simultaneous plasma urea concentration. The findings are not in agreement with the current concept for the mechanism of urea excretion in mammals. It is concluded that the renal tubules must either vary their permeability to urea in a highly selective manner or secrete urea actively.

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