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PubMed1998

Inter and intra-individual variations in urinary excretion of pyridinium crosslinks of collagen in healthy young adults.

OBJECTIVES: To investigate the inter- and intra-individual variation in the excretion of pyridinium crosslinks of collagen in first morning void urine samples in healthy young adults. DESIGN: An observational study in which urinary pyridinium crosslinks of collagen were measured in fasting first void urine samples over five consecutive days. SETTING: The study was conducted in the Department of Nutrition, University College, Cork, Ireland. SUBJECTS: A total of 17 healthy young adults (11 females and 6 males) aged 22-26 y were recruited from University College, Cork. The subjects were without any history of bone or articular disease, and with no intake of medicine that could affect bone or cartilage metabolism. RESULTS: There were large intra-individual variations in the excretion of both pyridinoline (Pyr) and deoxypyridinoline (Dpyr) in first morning void urine samples and the ratios of intra- to inter-individual variation were high. In comparison, inter-individual variation in excretion of crosslinks was relatively low. No significant day-to-day variation was observed either in Pyr or Dpyr excretion when either five, four or three consecutive days or four or three non-consecutive days of urine sampling were used. However, there were significant differences between any two consecutive or non-consecutive days in both Pyr and Dpyr excretion. CONCLUSIONS: The relatively large day-to-day variation in urinary excretion of the pyridinium crosslinks emphasises the need to use multiple samples to characterise the crosslink excretion of an individual. The present study demonstrates that urine sampling for these crosslinks necessitates at least a 3 d collection to ensure that day-to-day effects are not a significant source of variation included in the data analysis.

Adult↗
PubMed2001

Short-term effects of a hypocaloric diet on nitrogen excretion in morbid obese women.

OBJECTIVE: To determine whether the daily pattern of urine excretion of N wastes is affected by obesity and very low-calorie diets (VLCD). DESIGN: The plasma amino acid, urea and other energy parameters, as well as the urinary excretion of total nitrogen, urea and creatinine were studied in obese and normal-weight women. The obese women's data were obtained under hospital basal controlled conditions (8.1 MJ/day) and after 3 days of VLCD diet (1.9 MJ/day) controls were studied only once (5.8 MJ/day). The hourly excretion patterns of total N, urea and creatinine were determined from the composition of each bladder voiding. SUBJECTS: Twenty morbidly obese and 10 age-matched normal-weight control women. RESULTS: Plasma amino acid levels were higher in obese women, which showed a limited ability to metabolize amino acid hydrocarbon skeletons. Neither differences in the patterns between groups nor total 24 h values for urine volume were found. Total N and urea excretion diminished under VLCD diet. Hourly creatinine excretion showed a flat pattern and was higher in obese women than in the controls, VLCD diet diminished the amount of creatinine excreted in 24 h. CONCLUSIONS: The early change in energy availability that the creatinine excretion figures reflect may result from the energy conservation mechanisms induced in response to energy restriction. The early onset of this effect (3 days, and the extent of decrease (approximately 19%) also suggest that the impact of VLCD on the muscle energy budget of the obese is more marked than usually assumed.

Adult↗
PubMed2002

Effect of tamarind ingestion on fluoride excretion in humans.

OBJECTIVE: To evaluate the effect of tamarind (Tamarindus indicus) ingestion on excretion of fluoride in school children. DESIGN: Randomized, diet-control study. SUBJECT: Twenty healthy boys were included and 18 of them completed the study. INTERVENTIONS: Each subject consumed 10 g tamarind daily with lunch for 18 days at the social welfare boys' hostel. The nutrient composition of the daily diet was constant throughout the experimental period. RESULTS: Tamarind intake led to significant increase (P<0.001) in the excretion of fluoride in 24 h urine (4.8+/-0.22 mg/day) as compared to excretion on control diet (3.5+/-0.22 mg/day). However, excretion of magnesium and zinc decreased significantly (7.11+/-1.48 mg of Mg and 252.88+/-12.84 microg of Zn per day on tamarind diet as compared to 23.39+/-3.68 mg of Mg and 331.78+/-35.31 microg Zn per day on control diet). Excretion of calcium and phosphorous were not significantly different while creatinine excretion decreased with tamarind intake (225.66+/-81 mg creatinine/day with tamarind and 294.5+/-78.76 mg creatinine/day without tamarind). CONCLUSION: Tamarind intake is likely to help in delaying progression of fluorosis by enhancing urinary excretion of fluoride.

Child↗
PubMed2006

Urinary isoflavonoid excretion and soy consumption in three generations of Japanese women in Hawaii.

OBJECTIVE: To explore soy intake and urinary isoflavonoid excretion within several generations of American-Japanese women based on the hypothesis that earlier generations excrete higher levels of urinary isoflavonoids, in particular the metabolite equol, than later generations. SUBJECTS: A convenience sample of 43 women from 19 families aged 18-78 years, all of whom reported at least 50% Japanese ancestry. INTERVENTIONS: Each woman collected overnight urine samples at baseline and after consuming one serving of soymilk, both samples were analyzed for the isoflavonoids daidzein, genistein and equol using liquid chromatography-mass spectrometry. RESULTS: Median isoflavone intakes during the last year were 7.2 mg/day for the first generation, 7.3 mg/day for the second generation and 6.3 mg/day for the third generation (P=0.36). At baseline, the median isoflavonoid excretion for the first generation was nonsignificantly higher than for later generations (190, 86 and 42 nmol/h; P=0.20) but after intervention, the median urinary isoflavonoid excretion was very similar for the three groups: 2465, 1895 and 2775 nmol/h (P=0.70). Following intervention, a nonsignificantly higher proportion of older than younger women (53 vs 32 and 33%; P=0.41) excreted the metabolite equol. The respective median equol excretion rates by generation following intervention were 39.5, 4.2 and 3.5 nmol/h (P=0.04). CONCLUSIONS: This small investigation among three generations of Japanese-Americans detected a higher equol production among older women after a soy challenge, but no difference in the excretion of total isoflavonoids after a standardized dose of soymilk was observed.

Adolescent↗
PubMed1998

Blood pressure and diurnal variation in sodium, potassium, and water excretion.

The objective of this study was to examine associations of blood pressure (BP) with ratios of overnight to 24-h urinary excretion of sodium, potassium, and water. Each of 125 men 27-64 years of age, not taking diuretics, had BP measured during the day on a Monday. Beginning Monday evening, each participant provided three carefully timed 24-h urine collections, divided into daytime and overnight (bedtime to awakening) specimens. Proportion of total 24-h excretion of sodium, potassium, and water in the overnight specimen, standardised for creatinine excretion, was determined for each 24-h period. Associations of systolic and diastolic BP (SBP/DBP) with these proportions were examined with control for age, body mass index, alcohol intake, and heart rate. Mean BP was 116/71 mm Hg; 15 men were on non-diuretic anti-hypertensive therapy. Mean 24-h urinary excretion was 168 mmol for sodium, 68 mmol for potassium, and 16 mmol for creatinine. Mean overnight to 24-h proportions averaged over the 3 days were 30.7% for sodium, 22.0% for potassium, 32.1% for urinary volume, and 33.2% for creatinine. Partial correlations of SBP and DBP with the 3-day averages were 0.257 (P < 0.01) and 0.210 (P < 0.05) for sodium; 0.223 (P < 0.05) and 0.222 (P < 0.05) for potassium; 0.127 and 0.091 for urinary volume; and -0.033 and 0.014 for creatinine. Correlations for sodium proportions were larger for the first 24-h period, compared to the second or third 24-h period. These results indicate that higher BP was associated with a relatively greater proportion of sodium and potassium excretion at night. Further work is needed to clarify temporal sequence, ie, whether a relatively greater sodium and potassium excretion at night is a risk factor for higher BP (eg, via renal mechanisms), or whether higher BP results in relatively greater sodium and potassium excretion at night, or both.

Adult↗
PubMed2001

Urinary albumin excretion in lean, overweight and obese glucose tolerant individuals: its relationship with dyslipidaemia, hyperinsulinaemia and blood pressure.

The presence of microalbuminuria has become an important tool for therapeutic intervention. In this study we investigated whether the dysmetabolic syndrome of obesity was associated with or could occur in the absence of microalbuminuria. The study was conducted in 71 clinically healthy, glucose tolerant Hispanics (age: 43 +/- 1.4 years, body mass index (BMI): 28.7 +/- 0.6 kg/m(2), systolic blood pressure (SBP): 117 +/- 2 mm Hg, diastolic blood pressure (DBP): 77 +/- 1.3 mm Hg, urinary albumin excretion: 10.2 +/- 0.6 mg/24 h). Subjects were classified as lean (BMI <25), overweight (BMI >25 <30) and obese (BMI >30 kg/m(2)). Greater BMI was associated with higher body weight, waist-to-hip ratio (WHR), BP, fasting insulin, triglyceride, post glucose load insulin and glucose, and lower high-density lipoprotein (HDL) cholesterol levels. However, no significant differences in the urinary albumin excretion (mg/24 h) were found between lean (9.0 +/- 0.9; median: 9.1), overweight (11.3 +/- 1.2; median: 10.5) and obese (11.1 +/- 1.2; median: 9.7) subjects. In addition, microalbuminuria (urinary albumin excretion >30 mg/24 h) was not found in any of the study subjects. For all subjects combined, as well as for each of the groups separately, the urinary albumin excretion was unrelated to the BMI, WHR, body weight, triglyceride, cholesterol (total, LDL or HDL), fasting or post-load glucose and insulin plasma concentrations. Neither in females nor in males, abdominal fat accumulation was associated with an increase in the urinary albumin excretion. However, in the obese groups, urinary albumin excretion was strongly related to the level of SBP (r(2): 0.67; P < 0.0001) and DBP (r(2): 0.55; P < 0.0001). In summary, obesity, hyperinsulinaemia and dyslipidaemia per se are not determinants of increased albumin excretion. However, in the obese subjects, the BP, particularly the SBP, was a strong determinant of the level of albumin in the urine. Microalbuminuria may occur later in the course of the dysmetabolic syndrome, due to worsening of hypertension and development of hyperglycaemia.

Adult↗
PubMed1971

Studies on flavonoid metabolism. Biliary and urinary excretion of metabolites of (+)-(U- 14 C)catechin.

1. The biliary and urinary excretion of (+)-[U-(14)C]catechin was studied in normal male rats after a single injection of the flavonoid. 2. In rats large amounts of radioactivity (33.6-44.3% of the dose in 24h) were excreted in the bile as two glucuronide conjugates [one of which was a (+)-catechin conjugate] and three other unconjugated metabolites. 3. Excretion of radioactivity in the urine when the bile duct was not cannulated amounted to 44.5% of the dose. 4. In both the urine and bile the new metabolites showed maximum excretion in the (1/2)-1(1/2)h after intravenous injection of [(14)C]catechin. 5. The metabolites m-hydroxyphenylpropionic acid, p-hydroxyphenylpropionic acid, delta-(3-hydroxyphenyl)-gamma-valerolactone and delta-(3,4-dihydroxyphenyl)-gamma-valerolactione originate from the action of the intestinal micro-organisms on the biliary-excreted metabolites of (+)-catechin. These phenolic acid and lactone metabolites are then reabsorped and excreted in the urine. 6. It is proposed that, depending on the route of administration of (+)-catechin, there exists an alternative pathway, involving biliary excretion, for the metabolism of (+)-catechin.

Animals↗
PubMed1986

Excretion of laccase by sycamore (Acer pseudoplatanus L.) cells. Effects of a copper deficiency.

Copper-deprived sycamore (Acer pseudoplatanus) cells do not excrete molecules of active laccase in their culture medium. In the range of 2-100 micrograms of copper initially present per litre of nutrient solution, the total laccase activity measured in the cell suspensions at the end of the exponential phase of growth was closely proportional to the amount of added copper. However, copper-deprived cells excreted the laccase apoprotein (laccase without copper) at the same rate as copper-supplied cells excreted the active, copper-containing, laccase. When the culture medium was initially supplied with limiting amounts of copper, the active laccase was excreted until all copper molecules were metabolized. Thereafter, the laccase apoprotein was excreted. Consequently, at the end of the exponential phase of growth, the cell supernatants contained a mixture of apoprotein and copper-containing laccase. After purification and concentration, this mixture of copper-containing laccase (blue) and laccase apoprotein (slightly yellow) showed a yellow-green colour. Under copper-limiting culture conditions an equivalent decrease of Type 1, Type 2 and Type 3 Cu2+ was observed. Addition of copper to copper-deficient enzyme solutions does not result in a recovery of the enzyme activity. However, when added to copper-deficient sycamore-cell suspensions, copper induced a recovery of the excretion of active enzyme, at a normal rate, within about 10 h. The first molecules of active laccase were excreted after 3-4 h.

Apoenzymes↗
PubMed1975

Plasma uric acid concentration related to the urinary excretion of aldosterone and of electrolytes in normal subjects.

1. The relations between the concentration of plasma uric acid and urinary excretion of aldosterone, sodium and potassium, were studied in ten healthy males on a diet containing 160 mmol of sodium and 90 mmol of potassium per day. 2. Plasma uric acid correlated positively with aldosterone excretion and this correlation was statistically independent of sodium and potassium excretion. 3. Plasma uric acid correlated positively with potassium excretion and negatively with the urinary sodium/potassium ratio. There was no significant simple correlation with sodium excretion but the partial correlation of plasma uric acid and sodium excretion was negative and significant when excretion of aldosterone and potassium were held constant.

Adult↗
PubMed1978

Urinary dopamine in man and rat: effects of inorganic salts on dopamine excretion.

1. Plasma and urine free dopamine (3,4-dihydroxyphenethylamine) were measured in six normal male volunteer subjects and the urinary clearance of dopamine was calculated for each subject. 2. The excretion rates for free dopamine in man were greater than could be explained by simple renal clearance. It was concluded that free dopamine must, therefore, be formed in the kidney. 3. Changes in urinary dopamine excretion were studied in four groups of rats initially maintained on low sodium diet and then given equimolar dietary supplements of NaCl, NaHCO3, KCl or NH4Cl, to study the specificity of the previously observed increase in dopamine excretion after increased dietary NaCl. 4. The mean dopamine excretion increased significantly in rats given NaCl, KCl and NH4Cl, whereas dopamine excretion decreased in those given NaHCO3. 5. The failure of dopamine excretion to rise in response to loading with NaHCO3 was unexpected, and argues against a simple effect of volume expansion by the sodium ion. The increase in dopamine excretion with KCl and NH4Cl showed that this response was not specific to the sodium ion.

Adult↗
PubMed1986

The effect of sodium bicarbonate on the flow-dependency of urinary prostaglandin excretion in man.

The influence of oral water loading on the excretion rate of prostaglandin (PG) E was investigated in healthy human subjects in a control study where the urine was acidic (pH 5.7) and after oral sodium bicarbonate, which made the urine mildly alkaline (pH 7.2). PGE was immediately extracted from urine and measured by a radioimmunoassay technique. After sodium bicarbonate (5 g) the urinary PGE excretion rate was some three-fold higher (P less than 0.01) than in the control study, in the absence of any significant difference in the urine flow (approximately 80 ml/h). In the control study (urine pH 5.7) the urinary PGE excretion rate increased significantly (P less than 0.01) as the urine flow rose in response to the oral fluid load. However, after sodium bicarbonate, PGE excretion did not alter after the fluid load despite a 10-fold increase in urine flow. Since after bicarbonate administration PGE excretion is independent of urine flow, mildly alkaline urine may represent a condition under which renal PGE synthesis can be effectively assessed from measurements of urinary PGE excretion, in the presence of changes in urine flow. In addition, the results are compatible with the hypothesis that, in man, PGE may be passively reabsorbed in the distal nephron, and a reduction in this reabsorption could contribute to or be responsible for the dependency of the excretion rate of PGE on urine flow.

Adult↗
PubMed1989

Urinary excretion of dihydroxyphenylalanine and dopamine during alterations of dietary salt intake in humans.

1. Urinary excretion of dopamine (DA) increases during dietary salt loading. The majority of urinary DA is derived from circulating dihydroxyphenylalanine (dopa). Whether the increase in urinary DA excretion during salt loading results from increased efficiency of uptake of dopa by proximal tubular cells of the kidney, facilitation of intracellular conversion of dopa to DA, or increased delivery of dopa to tubular uptake sites, has been unknown. 2. In 10 inpatient normal volunteers on a constant diet, daily excretion of dopa and DA was assessed during normal sodium intake (109 mmol/day) for 1 week, low sodium intake (9 mmol/day) for 1 week and high sodium intake (249 mmol/day) for 1 week. 3. Urinary DA excretion exceeded urinary dopa excretion by about tenfold, and the excretion of both DA and dopa increased by about twofold between the low and high salt diets, with similar proportionate changes. Plasma dopa was unchanged by dietary salt manipulation. 4. The results indicate that increases in urinary DA excretion during dietary salt loading can be accounted for by increased delivery of dopa to sites of uptake by proximal tubular cells. Since dopa is released into the bloodstream by sympathetic nerve endings and by the brain, and since interference with decarboxylation of dopa attenuates natriuretic responses, dopa may function indirectly as a neurohormone involved in homoeostatic regulation of sodium balance.

Adult↗
PubMed1991

Differential effects of atrial natriuretic peptide and dopamine on urinary protein excretion in chronic glomerulonephritis.

1. To examine whether or not atrial natriuretic peptide-induced proteinuria simply results from increases in urine flow or glomerular filtration rate, we infused dopamine (1 microgram min-1 kg-1) and alpha-human atrial natriuretic peptide (0.025 microgram min-1 kg-1) into nine patients with chronic glomerulonephritis and nine essential hypertensive patients without renal damage, and compared the effects of the two agents on renal function and urinary protein excretion. 2. In patients with chronic glomerulonephritis, dopamine infusion significantly increased urinary sodium excretion (+59%), renal blood flow (+20%) and creatinine clearance (+14%). However, urinary protein excretion was not changed. Addition of atrial natriuretic peptide to the dopamine infusion further increased urinary sodium excretion and maintained creatinine clearance at the same level. In contrast to the infusion of dopamine alone, atrial natriuretic peptide markedly increased urinary protein excretion (77 versus 229 mg min-1 m2, P less than 0.02). Furthermore, the addition of atrial natriuretic peptide elevated the urinary protein/creatinine ratio (1.55 versus 5.35, P less than 0.05), while dopamine alone did not (1.55 versus 1.45, not significant). 3. In essential hypertensive patients, dopamine and dopamine plus ANP showed renal effects similar to those of chronic glomerulonephritis; however, the urinary excretion of protein was not changed significantly. 4. These results suggest that atrial natriuretic peptide may increase urinary protein excretion mainly by increasing the permeability of the damaged glomeruli to protein rather than by simply increasing urine flow or glomerular filtration. Possible mechanisms underlying the proteinuria-increasing effects of atrial natriuretic peptide are discussed.

Adult↗
PubMed1991

Effect of a single test dose of lithium carbonate on sodium and potassium excretion in man.

1. The possible natriuretic and kaliuretic effects of a single dose of lithium, as used in lithium clearance studies, were investigated in 15 healthy subjects on fixed sodium (100 mmol/24 h) and potassium (70 mmol/24 h) intakes. Lithium carbonate (300 mg or 600 mg) or placebo tablets were administered, double-blind and in random order, midway through a 48 h urine collection (divided into six 8 h periods), at 23.00 hours. 2. During the three 24 h periods which preceded the administration of lithium or placebo (control days), rates of sodium and potassium excretion followed normal circadian patterns, but no differences in excretion rates between the 3 control days were observed. Placebo tablets did not affect excretion rates. 3. After the 300 mg dose of lithium carbonate, 24 h sodium excretion increased by approximately 17 mmol (P less than 0.05); almost all of the natriuretic effect occurred during the first two 8 h periods. No effect on potassium excretion was observed. 4. After the 600 mg dose of lithium carbonate, 24 h sodium excretion increased by approximately 48 mmol (P less than 0.001) and 24 h potassium excretion increased by approximately 19 mmol (P less than 0.01). These effects were confined to the first two 8 h periods and thus occurred before and during the usual lithium clearance period. 5. Plasma renin activity, measured in 10 subjects, increased after the 600 mg dose of lithium carbonate (P less than 0.005), but plasma concentrations of aldosterone and atrial natriuretic peptide were not significantly affected. Neither the 300 mg dose of lithium carbonate nor the placebo tablets affected hormone levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2003

Diurnal variation in the renal excretion of modified RNA catabolites in humans.

Renally excreted modified RNA catabolites [pseudouridine (psi), N (2), N (2)-dimethylguanosine (m(2)(2)G) and N (6)-threoninocarbonyladenosine (t(6)A)] are markers of whole-body rates of degradation of rRNA and tRNA, and are thought to be potential indicators of the resting metabolic rate. To investigate diurnal variations of these RNA catabolites, the amounts of psi, m(2)(2)G and t(6)A excreted were determined by HPLC of the urine from eight healthy male adults collected over 47-h periods, which were subdivided into the morning (06.00 or 09.00 to 12.00 hours), the afternoon (12.00 to 18.00 hours), the evening (18.00 to 24.00 hours) and the night (00.00 to 06.00 or 08.00 hours), under two different nutritional regimens with 100 or 50 g of protein/day. Furthermore, rates of degradation of rRNA and tRNA were calculated using values for these RNA catabolites. For comparison, the corresponding excretion of creatinine, which originates from the energy metabolism of muscle, and of 3-methylhistidine (m(3)His), which is an indicator of muscle protein degradation, was determined. Differences in excretion during the collection periods were tested using the Friedmann test. The excretion of psi, creatinine and m(3)His (micromol x h(-1) x kg(-1)) altered significantly (P <0.001) during the day. Medians were: for psi, 0.21 (morning), 0.19 (afternoon), 0.19 (evening) and 0.18 (night); for creatinine, 8.8, 8.4, 8.0 and 7.3 respectively; for m(3)His, 0.13, 0.11, 0.12 and 0.10 respectively. The excretion rates of m(2)(2)G and t(6)A (nmol x h(-1) x kg(-1)) altered, but not significantly, during the day; corresponding medians were: for m(2)(2)G, 9.0, 8.4, 8.0 and 8.4 respectively; for t(6)A, 4.3, 4.1, 3.9 and 3.9 respectively. From these results it can be concluded that, in order to assess the average daily rates of degradation of tRNA and rRNA using modified RNA catabolites, urine collection should be carried out quantitatively over 24 h periods. Likewise, the catabolites creatinine and m(3)His must be determined using 24 h urine samples when average daily excretion values are required.

Adenosine↗
PubMed2002

The excretion of cephem antibiotics into saliva is inversely associated with their plasma protein-binding activities.

BACKGROUND: The excretion of medicated drugs into saliva may disturb the oral environment and antibiotic excretion into saliva appears to be regulated by many factors that have not been fully explored. METHODS: Excretion of four cephem antibiotics into saliva was examined in healthy volunteers and rats, using high-performance liquid chromatography, and the relationship between excretion levels and plasma protein-binding activities of the antibiotics was investigated. RESULTS: Following addition of 50 microgram/ml of each antibiotic to human plasma, protein binding rates (PBRs) of cefuzonam (CZON, molecular weight (MW): 535.58), cefotaxime (CTX, MW: 477.45), flomoxef (FMOX, MW: 518.45) and cefozopran (CZOP, MW: 551.99) were 87.8 +/- 1.2, 70.8 +/- 0.8, 36.2 +/- 0.5 and 8.3 +/- 0.3%, respectively. In rat plasma, PBRs of the four antibiotics were 94.0 +/- 0.5, 62.1 +/- 1.4, 54.0 +/- 0.8 and 6.0 +/- 0.8%, respectively. Similar PBRs were observed when the antibiotic concentration was increased to 100 and 200 microgram/ml. CZOP was most rapidly excreted into saliva and had the highest concentration in saliva among the tested antibiotics, while the plateau level of CZON was the lowest. The excreted levels of each antibiotic in saliva, when locally perfused through the rat facial artery, were inversely associated with each PBR. Similarly, the ratios of antibiotic concentration in saliva to rat plasma were almost constant for each antibiotic, revealing an inverse relationship with PBRs. CONCLUSION: These results appear to indicate that low molecular weight antibiotics are excreted into saliva through passive diffusion, inversely relating to their PBRs, and that high concentrations of antibiotics in the saliva have the potential to change the oral ecological environment.

Adult↗
PubMed1996

Phosphate and cyclic AMP excretion decreases during less than 12 hours of hypoxia in conscious rats.

Hypocapnia is known to have an antiphosphaturic effect that overcomes the phosphaturic effect of hypoxia. The objective of this study was to examine whether conscious rats exposed to acute hypoxia show a decrease in phosphate excretion due to the concomitant hypocapnia. Wistar rats weighing 200 g were exposed to hypoxia (inspired oxygen fraction = 0.10) or normoxia (inspired oxygen fraction = 0.21) for 6 h; and rats were alternately exposed to hypoxia or normoxia every 12 h for a total 36 h. Renal clearance and hormone studies were performed. Rats exposed to 6 h of hypoxia (n = 11) showed significant hypophosphaturia and decreases in absolute and fractional excretion of phosphate (0.38 +/- 0.10 microgram min-1, mean +/- SE, P < 0.0001 and 0.59 +/- 0.15%, P < 0.0001) as compared with normoxic rats (n = 11, 3.91 +/- 0.68 micrograms min-1 and 5.62 +/- 0.85%). In addition, nephrogenous adenosine 3',5'-cyclic monophosphate level per glomerular filtrate was significantly decreased (-0.87 +/- 0.64 nmol dL GF-1, P < 0.05) and plasma parathyroid hormone level was unchanged (45.2 +/- 9.5 pg mL-1) after 6 h of hypoxia as compared with normoxic rats (4.03 +/- 1.83 nmol dL GF-1 and 54.3 +/- 10.4 pg mL-1). A parallel increase in urinary noradrenaline and a decrease in dopamine excretion was observed in rats after 6 h of hypoxia. The decreased phosphate and adenosine 3',5'-cyclic monophosphate excretion during acute hypoxia were restored to normoxic levels by reoxygenation with 21% oxygen in the study of 12-h intermittent hypoxia. In summary, (1) hypoxia produced by inhalation of 10% oxygen for 12 h or less causes reduced phosphate and adenosine 3',5'-cyclic monophosphate (cAMP) excretion by spontaneously breathing rats; (2) these effects are reversed by reoxygenation and (3) hypoxia elicits a parallel increase in noradrenaline excretion and a decrease in dopamine excretion. These data suggest that renal adrenergic and dopaminergic systems play important roles in hypophosphaturia during acute hypoxia in conscious rats.

Animals↗
PubMed2000

Inositol hexakisphosphate in urine: the relationship between oral intake and urinary excretion.

OBJECTIVE: To study the relationship between the oral intake of inositol hexakisphosphate (InsP6, phytic acid, an inhibitor of urinary crystallization) and its urinary excretion, to establish their possible mutual influence. MATERIALS AND METHODS: Two groups of male Wistar rats (six animals each) received either; tap water and normal rat food pellets (controls); or a liquid diet in which InsP6 was absent and which then received gradually increasing amounts of InsP6. The urinary levels of InsP6 were then assessed regularly in both groups. RESULTS: When InsP6 was absent from the diet, urinary excretion declined to undetectable levels after 22 days. The addition of increasing amounts of InsP6 to the liquid diet caused an increase in its urinary excretion after about 10 days. Adding InsP6 in amounts > 425 mg/L caused no further increases in urinary excretion. Adding inositol (with no InsP6) to the liquid diet caused only a slight increase in the urinary excretion of InsP6. CONCLUSION: These results showed that InsP6 urinary levels were related to its oral intake; consequently, a low consumption of InsP6 would cause a urinary deficit of this crystallization inhibitor and thus an increase in the risk of developing urinary calcium stones. Although urinary excretion was dose-dependent, there was an ingested amount (20.9 mg/kg) above which there was no increase in the amount excreted. This intake is easily obtained by consuming a normal diet (rich in InsP6) indicating that to maintain appropriate urinary levels of InsP6, the consumption of InsP6 supplements is only necessary when the diet is particularly poor in InsP6.

Administration, Oral↗