Urinary Urea Excretion Research Articles

Apparent compartmentation of body nitrogen in one human subject: its consequences in measuring the rate of whole-body protein synthesis with 15N.

The rate of protein synthesis in the whole body was measured in one fed subject with seven 15N-labelled amino acids (intravenous and oral doses) and two 15N protein mixtures (oral doses only). The rates were determined individually from the urinary excretion of ammonia and total urea over a 12 h experimental period. Except with oral glycine and alanine, the synthesis rates given by ammonia and urea were appreciably different within each study when calculated on the assumption of a single pool of metabolic nitrogen in the body. In general, intravenous administration of the tracers gave higher rates with urea and the oral route gave higher rates with ammonia. The differences between intravenous and oral doses of 15N could be reduced significantly by calculating synthesis rates from either the arithmetic or harmonic average of flux rates given by ammonia and urea. The averages correspond to estimates of the total flux in a two-pool model of metabolic nitrogen when it is assumed either that both pools receive an equal amount of tracer (arithmetic) or that both have the same rate of nitrogen turnover (harmonic). By so reducing the effect of physical separation of nitrogen in the body, the metabolic aspects of compartmentation of the tracer could be examined. The results show that the absolute value obtained for protein synthesis depends on the source of labelled nitrogen. The data are discussed in this empirical context.

An Evaluation of Threonine and Isoleucine as the Third and Fourth Limiting Amino Acids in Corn for Growing Swine

Summary A metabolism experiment and two growth experiments were conducted to determine if threonine and isoleucine are the third and fourth limiting amino acids in corn for growing swine. In each experiment there were four dietary treatments. The basal diet contained corn fortified with minerals, vitamins, lysine and tryptophan. Threonine additions of 0 or .17% and isoleucine additions of 0 or .22% of the diet were evaluated in a 2  2 factorial arrangement of treatments. The addition of threonine reduced (P<.001) the daily urinary excretion of urea N and total N. There was a tendency for urea N excretion to be reduced further when isoleucine was added in combination with threonine. Addition of threonine alone improved (P<.05) feed efficiency and tended to increase weight gain and reduce feed intake. Isoleucine addition did not significantly affect any performance criteria. When threonine and isoleucine were added together, performance was poorer than when threonine was added alone. Plasma urea concentrations were reduced (P<.001) when threonine was added either alone or in combination with isoleucine. Isoleucine addition alone did not affect plasma

Changes in the urinary constituents in rats with chronic renal failure during oral administration of rhubarb extract.

The effect of rhubarb extract on the urinary constituents was examined in rats with chronic renal failure induced by adenine. Orally administered rhubarb extract caused a significant decrease in the urinary excretion of urea. The amount of urinary Na, K, and Ca was significantly reduced in the rhubarb extract-treated rats, while urinary inorganic phosphate was significantly elevated. A polyuria-preventive effect was observed. However, there was no marked change in the amount of urinary creatinine throughout the experimental period. The mechanism of uremia-improving action of rhubarb extract is discussed on the basis of the present results and the previously reported data [Chem. Pharm. Bull., 32, 4506 (1984)].

Atrophy and growth failure of rat hindlimb muscles in tail-cast suspension.

Atrophy and growth failure of muscle in a tail-cast suspension model were evaluated in hindlimbs of female Sprague-Dawley rats. Based on measurements of food consumption, animal growth rate, urinary excretion of urea and ammonia, and muscle size, 6 days seemed to be the optimum duration of suspension for studying muscle unloading. After 6 days, the soleus, plantaris, and gastrocnemius muscles from suspended animals were 27, 10, and 11% smaller (P less than 0.05), respectively, than those from tail-casted weight-bearing animals. The extensor digitorum longus and tibialis anterior muscles were unaffected by suspension (less than or equal to 6 days) while the triceps brachii hypertrophied (8%, P less than 0.05). Wet weight-to-dry weight ratios were smaller in the plantaris (-0.19, P less than 0.05) and gastrocnemius (-0.19, P less than 0.05) muscles from suspended rats. In the plantaris, this difference coincided with a higher protein concentration (+12 mg/g, P less than 0.001). In vitro measurements of protein metabolism in the soleus muscles of suspended rats showed both slower protein synthesis (P less than 0.05) and faster protein degradation (P less than 0.05), whereas these processes were unaltered in the extensor digitorum longus muscles.

Nutritive value and metabolic effects of whey protein concentrate and hydrolysed lactose for growing pigs

In two digestibility and balance trials with growing pigs, whey protein concentrate (WPC) was compared as a protein supplement with casein (CAS) and dried skim milk (DSM), and, 30 % lactose (40 % dried whey, DW) was compared as a sugar supplement with the same amounts of hydrolysed lactose (HYLA) and sucrose (SUC). The effects of these supplements on protein and mineral metabolism of the pigs were investigated, WPC contained 42.2 % crude protein and had a high content of lysine, 8.6 g, and sulphur containing amino acids: cystine 2.8 and methionine 2.2g/16 g N, These exceeded the values for DSM. The hydrolysing degree of the enzymatically treated lactose syrup was 73 %. WPC had high crude protein digestibility, 99.1 % as compared to 95.4 for CAS and 95.0 % for DSM. Dried whey had low crude protein digestibility, 72.5 %. The amino acids in the WPC diet were highly digestible, but low values were obtained for the DW diet. On the WPC diet, nitrogen retention was higher than with the other protein supplements (P &gt; 0.05), urinary urea excretion was low and the biological value very high. On a combination of WPC and HYLA protein utilisation was higher than on dried whole whey. On the diets supplemented with different sugars, none of the blood parameters differed statistically significantly (P &gt; 0.05) and all values lay within the reference range. Water intake was on average 49 % greater on diets with sugar supplements than without. Urinary excretion of reducing sugars averaged 40.2, 8.3 and 6.6 g/d on the HYLA, SUC and DW diets, while on the diets without sugar supplements the values were 0.8—1.2 g/d. The following mean daily mineral retention values were obtained: P 4.0 g, Ca 5,9 g. Mg 0,4 g, Na 1.9g, K 2.9 g, Fe 27 mg, Cu 6.4 mg, Zn 65 mg and Mn 4.0 mg. The surplus Na and K on the DW diet were excreted in the urine and the pigs did not have diarrhoea.

Urea synthesis after protein feeding reflects hepatic mass in rats.

Urea synthesis is an exclusive biosynthetic function of the liver. Since the exact relationship between urea synthesis in vivo and functional liver mass remains unclear, we established an animal model using oral protein loading and measurement of resultant urea synthesis in rats. We studied rats subjected to sham operation, 40% hepatectomy, 66% hepatectomy, portacaval shunt and CCl4-induced cirrhosis. Urea synthesis was calculated as the sum of urinary urea excretion and accumulation of urea in body water during the 6-hr period after oral administration of a casein protein load equivalent to 20 gm per kg body weight. Peak urea synthesis rate in the sham-operated group of rats was 142 +/- 11 mumoles per hr per gm wet liver weight (mean +/- 1 S.D.), 473 +/- 34 mumoles per hr per gm liver protein and 80 +/- 5 mumoles per hr per mg liver DNA. This rate closely matched those of the other groups for each type of liver mass measurement. Marked reduction (p less than 0.01) of urea synthesis on a DNA basis was noted only in the CCl4-cirrhotic livers, related to the significantly higher (p less than 0.01) DNA content of the cirrhotic livers. Similarly, increased (p less than 0.05) liver protein content of the sham-operated rats when compared with the other groups was reflected in slightly lower urea synthesis rates expressed on the basis of liver protein (p less than 0.05) when compared to that of all other groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced diabetogenic effect of streptozotocin in rats previously adapted to a high-protein, carbohydrate-free diet.

The diabetogenic effects of streptozotocin (STZ) (40 or 60 mg/kg body wt, i.v.) were examined in rats that had been previously fed either a high-protein, carbohydrate-free (HP) diet (70% protein, 8% fat) or a control diet (66% carbohydrate, 16% protein, 8% fat), and maintained on the same diets after drug injection. Rats on the HP diet 15-21 days before STZ administration showed reduced mortality and decreased severity of diabetes as judged by rate of body-weight change, plasma glucose, urine volume and glycosuria, serum and pancreatic insulin, and morphology of islets of Langerhans. In rats on the control diet, values for serum and pancreatic insulin did not differ 2 and 14 days after 40 mg/kg of STZ. In contrast, in rats under the HP regimen, serum insulin levels doubled 14 days after STZ and pancreatic insulin content was almost 20 times higher than at day 2. Rats previously fed on the HP diet for 21 days, but transferred to the control diet 2 days after STZ injection, also showed reduced severity of diabetes, as indicated by rates of body-weight gain, urinary excretion of urea, and levels of serum and pancreatic insulin. However, in these animals the effects of the HP diet were not as marked as those observed in the rats that were maintained on the HP diet after STZ injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal control of plasma urea level in sheep: the diuretic effect of urea, potassium and sodium chloride.

Two merino ewes were fed 800 and then 1000 g of lucerne chaff per day and renal responses and extracellular fluid volume (E.C.F.) were determined. Urine urea nitrogen, glomerular filtration rate (G.F.R.), urine volume, effective renal plasma flow (E.R.P.F.) and E.C.F. increased in both animals with the greater nitrogen intake. In a second experiment, five merino wethers and four merino ewes were infused intraruminally with increasing quantities of urea, whilst being fed a mainly roughage ration, and the above parameters were determined. No significant changes in G.F.R., E.R.P.F. or E.C.F. were noted. Urinary excretion maintained a linear response to nitrogen input until 20.6 g of urea nitrogen per day were infused. At this level of infusion, an increased fractional reabsorption of urea resulted in a large increase in plasma urea concentration, but when 500 mmol of NaCl or KCl were added to the infusate, urine urea nitrogen excretion increased from 10.4 to 11.4 and 11.9 g/d respectively and plasma urea concentration decreased from 68.0 to 35.2 and 37.3 mg nitrogen/100 ml. Urea clearance virtually trebled with both electrolyte infusions and E.C.F. and G.F.R. increased by approximately 10 and 25% respectively. It is concluded that urea alone has limited diuretic ability and that the increased electrolyte content of higher protein dry roughage diets aids urine urea excretion by increasing G.F.R., and the urine flow rate by an osmotic diuretic effect.

Urine composition in rats with adenine-induced renal failure during treatment with rhubarb extract.

The effect of rhubarb extract on the urinary constituents was examined in rats with renal failure induced by adenine. Administration of the rhubarb extract markedly increased the urinary excretion of both urea and creatinine, indicating an improvement of renal clearance in the uremic state. Furthermore, a number of significant differences in the amino acid levels in the urine were observed. Among the essential amino acids, the urinary outputs of threonine, phenylalanine, leucine, and methionine were remarkably lower in the rhubarb extract-treated group than in the control group. Outputs of inessential amino acids (alanine, glycine, glutamic acid, serine, aspartic acid, tyrosine, and cysteine) were also strikingly reduced after the treatment. In addition. the amount of urinary Ca was significantly reduced in the rhubarb extract-treated rats. while urinary inorganic phosphate was significantly elevated. A marked decrease of 2, 8-dihydroxyadenine excretion in the urine was noticed. However, no changes were seen in the urinary excretions of protein, glucose, Na, and K throughout the experimental period.

Metabolic Response of Whole Body and Peripheral Tissues to Enteral Nutrition in Weight-Losing Cancer and Noncancer Patients

This study evaluated whether or not the efficiency of utilizing energy substrates and nitrogen differs among cancer and control patients during enteral feeding. Oxygen uptake and glucose, lipid, and amino acid metabolism across the leg were measured in cancer patients who had lost approximately 18% of their body weight and were compared with that of patients without cancer with similar body-weight loss. Metabolic balances across the leg were evaluated relative to food intake, energy expenditure, energy balance, nitrogen balance, and urinary excretion of urea, creatinine, adrenaline, and noradrenaline. All measurements were performed twice in each patient: first in the fasted state and second during nutrition after 14 days of a controlled enteral infusion of a formula diet of 35 kcal/kg . day. Quantitative measurements of metabolism across the leg before and after 14 days of enteral nutrition were compared with changes in nutritional status. Whole body utilization of energy and of nitrogen were not significantly different among cancer patients and controls, whereas the simultaneously measured net balances of glycerol and free fatty acids across the leg of cancer patients were statistically significantly more negative during the constant infusion of the formula diet. The results in this study emphasize that malnourished cancer patients are quite comparable with patients with benign malnutrition in terms of whole body and peripheral metabolism both before and in the response to enteral feeding.

Losses in weight and body water in sows after weaning.

The loss of body water of eight sows in the 7 d following weaning was determined using the deuterium oxide dilution technique. Four of the sows had received a concentrate diet in restricted amounts while the other four had been given the same diet mixed with two-thirds its weight of oat husks ad lib. during the whole of the preceding lactation. Certain blood and urine constituents were also measured. Loss of body water was significantly less (P less than 0.05) than weight loss of fasted animals, but body water losses were considerable in six of the eight animals. Excretion of urinary nitrogen, urea and creatinine and levels of plasma urea were higher, while levels of plasma non-esterified fatty acids and the hydroxyproline index were lower 1 week after weaning compared with values obtained on the day following weaning. These results indicate that in addition to water loss, depletion of body tissue, including protein, occurs in the newly-weaned sow.

UREA METABOLISM IN STEERS FED MATURE GRASS HAY AND GIVEN FRESH OR SALT WATER

Four steers given 5.5 kg/day of mature mixed temperate species of grass hay at 2-h intervals and consuming either fresh water or water containing 1% (wt/vol) NaCl were used in a study of urea metabolism. 14C-urea and H14CO3− tracers were used to measure the rate of irreversible loss from the plasma urea pool and the rate of transfer of plasma urea to the rumen. Rate of excretion of urea in urine and degradation of plasma urea in the postruminal gastrointestinal tract were also measured. Despite a large increase in urinary volume there was no effect of salt water ingestion on urinary urea excretion or the amount and site of urea degradation in the gastrointestinal tract. On average the rate of irreversible loss of plasma urea was 36.1 g N/day, of which 9.7 g N/day were excreted in urine. Degradation in the rumen was 17.9 g N/day or 68% of total urea degradation, and this was equivalent to a clearance of urea to the rumen of 392 L/day. This transfer of plasma urea to the rumen was equal to 27% of dietary N intake. Transfer of plasma urea to the rumen was much more extensive than previously observed in cattle fed tropical forage diets, but was similar to that obtained in experiments with cattle fed tropical forage plus sugar, or sheep fed high intakes of bromegrass hay. Key words: Urea metabolism, salt

Effect of arginine, urea and .ALPHA.-aminoisobutyric acid on the urinary nitrogen excretion in adult chicks.

The relations among urinary excretion of dietary urea, metabolic one derived from arginine degradation and arginine and the effects of α-aminoisobutyric acid (AIB) on these relationships were studied using adult chicks with an artificial anus. In chicks fed the basal diet containing a normal amount of arginine, the urinary excretion of arginine was negligible. On the day when chicks were fed the excess arginine (2%) diet, urinary excretion of urea and arginine was highly increased. The excess feeding of arginine for the AIB-treated chicks further increased the excretion of urinary arginine and undetermined nitrogen, but the urea excretion was significantly lower than that of the excess arginine chicks. In chicks fed the 1% urea diet with or without AIB, a significantly higher excretion of urea and undetermined nitrogen was observed than those in the control chicks.These results showed that AIB has the following functions for arginine and urea excretion in chicks. (1) AIB supplemented to the excess arginine diet decreases the urea formation through suppression for kidney arginase activity. (2) AIB promotes the urinary excretion of excess dietary arginine by means of a depression of renal reabsorption of this amino acid. (3) When AIB is added to the 1% urea diet, this material gives no effect on urinary excretion of urea.

Diurnal variation in urine [15N]urea content, estimates of whole body protein turnover, and isotope recycling in healthy meal-fed children with cystic fibrosis.

The pattern of urinary urea excretion and labelling with 15N was examined in eight meal-fed 6 to 9 year old children, over a 3-day period using a simulated constant infusion of the label. The children had cystic fibrosis but were healthy and in a good nutritional status at the time of the study. Reciprocal diurnal patterns of urea excretion and [15N]urea enrichment were noted and found to be suitable for mathematical description. Urea excretion was maximal in the evening at approximately 2000 and minimal at 0800, whereas the [15N]urea enrichment was maximal at about 0800 and minimal at 2000. In addition to the diurnal variation the [15N]urea enrichment increased exponentially to a plateau or isotopic steady state. The diurnal variation in [15N]urea enrichment resulted in large diurnal changes in the calculated rates of whole body amino nitrogen flux, synthesis, and breakdown. Flux rates were approximately 44% higher in the evening than in the morning. Synthesis rates were 19% higher in the evening, whereas breakdown rates were 27% greater in the morning. Mean amino nitrogen flux rates were 1.28 (SD 0.13) . g N . kg-1 . day-1. Isotope recycling was estimated from the slope of the [15N]urea enrichment curve between 30 and 54 h from the start of the study. There was a wide range in recycling, 2.9 - 19.4% (mean 11.4, SD 5.4). Some of the biological and pharmacological importance of the diurnal variation in the protein metabolism is discussed.

Urea synthesis and degradation in sheep given pelleted-grass diets containing flaked barley.

1. Three sheep fitted with rumen and oesophageal cannulas were given hourly the following diets in successive experiments: 1000 g pelleted-grass cubes/d (diet A) and 700 g pelleted-grass cubes plus 300 g flaked barley/d (diet B).2.During the final week of each 4-week dietary regimen, a balance trial was conducted and on separate days each sheep was continuously infused with [14C]urea and NaH14CO3 intravenously and NaH14CO3 intraruminaily. C transfer rates between blood urea, blood bicarbonate and rumen bicarbonate pools were calculated from the specific radioactivity of urea and bicarbonate sampled and isotope infusion rate during each experimental period. In the same period, an oral infusion of 51Cr-EDTA was maintained and salivary flow rate and composition determined from samples collected from the oesophageal fistula.3. The inclusion of flaked barley in the pelleted-grass diet significantly (P &lt; 0·01) increased the apparent digestibility of organic matter (0·069), apparently digestible organic matter intake and nitrogen balance, and increased the efficiency cf dietary N utilization from 0·059 (diet A) to 0·290 (diet B). Increased N balance was the result of a significant (P) &lt; 0·01 reduction in urinary urea excretion.4. The rumen fluid of sheep given diet A had higher pH and bicarbonate concentrations but lower butyric acid concentrations than that of sheep given diet B. There was no significant effect of diet on total volatile fatty-acid or ammonia concentrations in rumen fluid, or on osmolaiity and rumen fluid dilution rate. The irreversible loss of bicarbonate from rumen fluid was markedly increased when flaked barley was included in the diet, with most of the loss occurring directly from rumen fluid.5. Sheep given diet A had higher salivary secretion rates (18·8 l/d) than those given diet B (12·7 l/d), and with the exception of urea, there was no effect of diet on the concentrations of total N, protein N, alpha;-amino-N, uric acid-N or bicarbonate in saliva. Urea concentrations in saliva were significantly correlated (r20·64) with blood urea concentrations, but not with salivary flow rate. Salivary secretions contributed 2·2 and 1·4 gN/d to the rumen of sheep given diets A and B respectively, with urea forming only 45–33% of the total N secreted.6. When flaked barley was included in the pelleted-grass diet, there was a significant (P &lt; 0·01) decrease in urea synthesis rate (diet A 20·0 g N/d, diet B 9·7 g N/d), a significant increase in amount (diet A 2·3 g N/d. diet B 3·0 g N/d) and proportion (diet A 0·024, diet B 0·57) of recycled urea degraded in the rumen. The permeability of the rumen wall to urea was also significantly increased in sheep given the flaked barley diet (diet A 1·35 g N/d, diet B 2·45 g N/d).7. A model of urea metabolism in sheep given each diet is described, and the mechanisms by which flaked barley inclusion increased urea recycling to the rumen and the efficiency of dietary N utilization are discussed.

The effects of intraruminal infusions of sodium bicarbonate, ammonium chloride and sodium butyrate on urea metabolism in sheep.

1. Three sheep fitted with rumen cannulas were fed hourly a daily ration of 1000 g pelleted-grass cubes, and during four successive 2-week periods were intraruminally infused (0·45 l/d) with solutions containing sodium chloride (0·47 mol/d), sodium bicarbonate (0·47 mol/d), ammonium chloride (0·47 mol/d) and sodium butyrate (0·47 mol/d). Each solution, except that for NaHCO3, was adjusted to pH 7 before infusion, and provided equal sodium intakes for sheep in all periods.2. In the final week of each infusion period, a balance trial was conducted and on separate days each sheep was continuously infused with [14C]urea and NaH14CO3 intravenously and NaH14CO3 intraruminally. Carbon transfer rates between blood urea, blood bicarbonate and rumen fluid bicarbonate were calculated from the specific radioactivity of urea and bicarbonate samples and isotope infusion rates during each experimental period.3. There was no significant effect of intraruminal infusions on N balance, and with the exception of sheep in fused with NH4Cl, all sheep utilized apparently digested N with similar efficiency for N retention. Sheep infused with NH4Cl (6·2 g N/d) excreted the equivalent of 93% of the infused N as urea in urine.4. Infusion of NaHCO3. NH4Cl and sodium butyrate significantly (P &lt; 0·05) increased the rurnen fluid concentrations of bicarbonate, ammonia and butyric acid respectively, and all infusions significantly (P &lt; 0·05) increased total volatile fatty acid concentrations. Both NaHCO3 and sodium, butyrate significantly (P &lt; 0·05) increased the pH of rumen fluid There was no significant effect of infusion on the proportions of propionic acid or the osmolality of rumen fluid.5. Intraruminal infusions of NH4Cl significantly (P &lt; 0·05) increased and infusion of sodium butyrate significantly (P &lt; 0·05) decreased plasma urea concentrations. Sheep infused with NH4Cl had higher rates of urea synthesis and urinary urea excretion compared with sheep on the other treatments, and a significantly (P &lt; 0·05) lower proportion of urea synthesized by these sheep was degraded in the digestive tract. Sheep infused with sodium butyrate degraded a significantly (P &lt; 0·05) greater amount (3·2 g N/d) and proportion (0·24) of total urea synthesis in the rumen than did sheep infused with NaCl. Corresponding values for the control (NaCl) sheep were 1·5 g N/d and 0·13 respectively. There was no significant effect of other infusions on the amount of urea recycled to the rumen or on the distribution of total urea degradation between the rumen and lower digestive tract. Plasma urea clearance to the rumen was significantly (P &lt; 0·05) increased during sodium butyrate infusion, and the clearance of urea to the lower digestive tract was significantly (P &lt; 0·05) decreased during NH4Cl infusion.6. The mechanism by which urea entry into the rumen is regulated by rumen metabolite levels is discussed.

Endocrinology and metabolism: an annotated bibliography of recent literature. References to journal articles and other papers.

Endocrinology and metabolism: an annotated bibliography of recent literature. References to journal articles and other papers.

Urinary urea: are currently available methods adequate for revival of an almost abandoned test?

Measurement of urinary urea excretion has been suggested as a means of estimating nitrogen balance in hospitalized patients who are malnourished. Because proficiency-testing surveys show gross variations in mean urea as determined by various automated methods and extremely poor precision occasionally, we compared urinary urea measurements and ammonia interference in three widely used methods. The coupled urease/glutamate dehydrogenase method (used in the DuPont aca) showed positive interference from ammonia, as expected; with the diacetylmonoxime (Technicon (12/60) and the urease conductivity (Beckman ASTRA) methods we saw no such interference. Generally, interference by ammonia is less than 10%, but (rarely) it may exceed 25%. However, if urine specimens are properly diluted and potential sources of interference recognized, all three methods appear capable of providing clinically useful data.

Quantification of acute cephaloridine nephrotoxicity in rats: Correlation of serum and 24-hr urine analyses with proximal tubule injuries

The nephrotoxic effect of one single iv injection of cephaloridine in rats was investigated. Urine and serum samples and kidneys were analyzed up to 24 hr after injection. The degree of kidney injury was determined by enumeration of the percentage of altered tubules of alkaline phosphatase-stained cryostat sections. The percentage of injury was compared with the urinary excretion of urea, creatinine, Na +, K +, Cl −, protein, aminopeptidase, alkaline phosphatase, and lactic dehydrogenase (LDH) and found to correlate best with LDH ( r = 0.94, p < 0.001, up to 1000-fold increases). No correlation was found with urea, creatinine, Na +, K +, and Cl − concentrations in serum 24 hr after injection or with the enzyme concentrations in kidney homogenates. Although isolation of rats in metabolism cages caused minor transient increases of lactic dehydrogenase and aminopeptidase excretion in the urine, it did not affect the correlation of injury and urinary enzyme content. This correlation still held when cephaloridine was injected at different times of the day. However, from such studies it became apparent that susceptibility of kidneys to the nephrotoxic effect of cephaloridine was dependent on a circadian rhythm with a maximum of susceptibility at 7 pm and a minimum at 7 am. Serum clearance of cephaloridine on the other hand was not dependent on a circadian rhythm. The nephrotoxic effect of cephaloridine can be measured best 24 hr after application by determination of the number of injured tubules in frozen sections stained for alkaline phosphatase and of kidney-derived lactic dehydrogenase excreted into the urine.

Dietary Minerals Modify the Food Intake Suppressing Effects of High Casein Diets Fed to Rats

Food intake, growth, and urinary urea and ammonia excretion were studied in young rats undergoing adaptation to high protein diets (70% casein) containing varying amounts of potassium, sodium and chloride. Two commercial mineral mixtures were used. The Bernhart-Tomarelli (BT) mineral mixture is low in K, Na and Cl compared to the TD (modified Williams-Briggs) mineral mixture. Rats consumed significantly less food and had poor growth when fed 70% casein diets containing the BT mineral mixture. Food intake and feed efficiency improved significantly when the BT diets were supplemented with KCl and NaCl, Na acetate or K acetate but not 3-chloropropionate. Urinary urea and ammonia excretion were directly proportional to food (protein) intake. However, body weight gain during the last 3 days of the 9-day study (experiment 3) was negatively correlated with urinary ammonia nitrogen (milligrams per gram food eaten) but not with urinary urea nitrogen. It is concluded that dietary K and/or Na content affects food consumption in rats fed high casein diets. Alterations in renal capacity for handling ammonia may be responsible for the food intake enhancing effect of K or Na in rats fed a high casein diet.high casein diet mineral mixture potassium sodium urinary ammonia food intake