A possible contribution of endogenous atrial natriuretic peptide to proteinuria in patients with chronic renal failure.

Plasma levels of immunoreactive atrial natriuretic peptide (IR-ANP) were measured with a specific radioimmunoassay in 19 undialysed patients with chronic renal failure. At the beginning, an extremely high level of plasma hANP (50 fmol/ml) seen in a patient was rejected with Smirnov's test and was excluded from further statistics. The plasma IR-ANP levels in these patients were significantly higher than those of 19 normal subjects matched with age and sex (10.9 +/- 1.6 vs 5.3 +/- 0.6 fmol/ml, mean +/- SEM, p less than 0.01), and positively correlated with mean blood pressure (r = 0.44, p less than 0.05) and the cardiothoracic ratio (r = 0.65, p less than 0.01), but did not correlate with creatinine clearance (r = -0.38, n.s.). Further, a significant correlation was observed between plasma IR-ANP and urinary protein output (r = 0.47, p less than 0.05). On the other hand, urinary protein output did not correlate significantly with variables such as mean blood pressure, the cardiothoracic ratio or creatinine clearance. Since it has been suggested that ANP enhances glomerular capillary permeability, increased ANP responding to volume overload in those patients may play an important role in increasing urinary protein excretion.     

Urinary excretion of immunoreactive prostaglandin F2 alpha in healthy children and adults

The 24-hours urinary excretion of immunoreactive prostaglandin F2 alpha (U-iPGF2 alpha) in normal children on a free diet was not significantly different in 30 boys (aged 3-15 years; geometric mean 589 ng/24 h) compared to 27 girls (aged 4-14 years; mean 473 ng/24 h). In both sexes this excretion rose with age until adolescence where it reached a plateau. In normal adults the men had significantly higher (p less than 0.001) excretions of U-iPGF2 alpha than the women; also body weight and urinary creatinine excretion were higher in men (p less than 0.001). In the children, as well as in the total population, U-iPGF2 alpha correlated best with body weight (r = 0.44 and r = 0.48 respectively; p less than 0.001) and the urinary creatinine excretion (r = 0.53 and 0.57 respectively; p less than 0.001); both body weight and urinary creatinine excretion are reflections of total body development. After the correction for urinary creatinine excretion or for body weight, the sex difference in the adult U-iPGF2 alpha totally disappeared.     

Genetic and dietary interactions: role of angiotensin AT1a receptors in response to a high-fructose diet

The renin-angiotensin system (RAS) has been implicated in the cardiovascular complications of diabetes. We showed that a high-fructose diet increases blood pressure and plasma angiotensin and impairs glucose tolerance. We investigated the role of angiotensin AT(1a) receptors in the development of fructose-induced cardiovascular and metabolic dysfunction. Male angiotensin AT(1a) knockout (AT1aKO) and wild-type (AT1aWT) mice with arterial telemetric catheters were fed a standard diet or one containing 60% fructose. Fructose increased mean arterial pressure (MAP) in AT1aWT but only during the dark phase (8% increase). In AT1aKO mice, fructose unexpectedly decreased MAP, during both light and dark periods (24 and 13% decrease, respectively). Analytical methods were used to measure systolic arterial pressure (SAP) and pulse interval (PI) variability in time and frequency domains. In fructose-fed AT1aWT mice, there was an increase in SAP variance and its low-frequency (LF) domain (11 +/- 3 vs. 23 +/- 4 mmHg(2), variance, and 7 +/- 2 vs. 17 +/- 3 mmHg(2), LF, control vs. fructose, P < 0.004). There were no changes in SAP variance in AT1aKO mice. Depressor responses to alpha(1)-adrenergic blockade were augmented in fructose-fed AT1a WT compared with AT1aKO mice. Fructose inhibited glucose tolerance with a greater effect in AT1aWT mice. Fructose increased plasma cholesterol in both groups (P < 0.01) and reduced ANG II in AT1aKO mice. Results document prominent interactions between genetics and diet with data showing that in the absence of angiotensin AT(1a) receptors, a fructose diet decreased blood pressure.     

Estrogen and salt sensitivity in the female mRen(2). Lewis rat

The present study determined whether early loss of estrogen influences salt-sensitive changes in blood pressure, renal injury, and cardiac hypertrophy as well as the effects on the circulating renin-angiotensin-aldosterone system (RAAS) in the hypertensive female mRen(2). Lewis strain. Ovariectomy (OVX) of heterozygous mRen(2). Lewis rats on a normal salt (NS) diet (0.5% sodium) increased systolic blood pressure from 137+/-3 to 177+/-5 mmHg (P<0.01) by 15 wk but did not show any changes in cardiac-to-body weight index (CI), proteinuria, or creatinine clearance. Maintenance with a high-sodium (HS) diet (4%) increased blood pressure (203+/-4 mmHg, P<0.01), proteinuria (3.5+/-0.3 vs. 6.4+/-0.7 mg/day, P<0.05), and CI (4.0+/-0.1 vs. 5.2+/-0.1 mg/kg, P<0.01) but decreased creatinine clearance (0.89+/-0.15 vs. 0.54+/-0.06 ml/min, P<0.05). OVX exacerbated the effects of salt on the degree of hypertension (230+/-5 mmHg), CI (5.6+/-0.2 mg/kg), and proteinuria (13+/-3.0 mg/day). OVX increased the urinary excretion of aldosterone approximately twofold in animals on the NS diet (3.8+/-0.5 vs. 6.6+/-0.5 ng.mg creatinine-1.day-1, P<0.05) and HS diet (1.4+/-0.2 vs. 4.5+/-1.0 ng.mg creatinine-1.day-1, P<0.05). Circulating renin, angiotensin-converting enzyme, and angiotensin II were also significantly increased in the OVX group fed a HS diet. These results reveal that the protective effects of estrogen apart from the increase in blood pressure were only manifested in the setting of a chronic HS diet and suggest that the underlying sodium status may have an important influence on the overall effect of reduced estrogen.     

Reduced natriuresis after oral sodium load in cholestatic rats: role of compartment volumes and ANP

The purpose of this study was to assess the participation of the atrial natriuretic peptide (ANP)-cGMP system in electrolyte and volume handling of cholestatic rats submitted to an acute oral sodium load. Cholestasis was induced by ligation and section of the common bile duct (n = 51). Control rats were sham operated (n = 56). Three weeks after surgery, 24-hr urinary volume, sodium, potassium, cGMP and creatinine excretion were measured. Three days later, animals received 10 mmol/kg NaCl (1 M) by gavage, and urinary excretion was measured for 6 hr. In parallel groups of rats, plasma volume, electrolytes and ANP concentration, extracellular fluid volume (ECFV), and renal medullary ANP-induced cGMP production were determined in basal conditions or 1 hr after oral sodium overload. As compared with controls, cholestatic rats had a larger ECFV and higher plasma ANP (67.2 +/- 5.2 vs 39.7 +/- 3.5 pg/ml), but lower hematocrit and blood volume, and were hyponatremic. Cholestatic rats showed higher basal excretion of sodium, potassium, and volume than controls, but equal urinary cGMP. After the NaCl overload, cholestatic rats showed a reduced sodium excretion but equal urinary cGMP. One hr after sodium overload, both groups showed hypernatremia, but whereas in control rats ECFV and ANP increased (50.7 +/- 4.1 pg/ml), in cholestatic rats ECFV was unchanged, and plasma volume and ANP were reduced (37.5 +/- 5.8 pg/ml). ANP-induced cGMP production in renal medulla was similar in cholestatic and control nonloaded rats (14.2 +/- 5.2 vs 13.4 +/- 2.6 fmol/min/mg). One hr after the load, medullary cGMP production rose significantly in both groups, without difference between them (20.6 +/- 3.1 vs 22.7 +/- 1. 7 fmol/min/mg). We conclude that the blunted excretion of an acute oral sodium load in cholestatic rats is associated with lower plasma ANP due to differences in body fluid distribution and cannot be explained by renal refractoriness to ANP.     

Urinary excretion of immunoreactive prostaglandin F2α in healthy children and adults

The 24-hours urinary excretion of immunoreactive prostaglandin F_2α (U-iPGF_2α) in normal children on a free diet was not significantly different in 30 boys (aged 3–15 years; geometric mean 589 ng/24 h) compared to 27 girls (aged 4–14 years; mean 473 ng/24 h). In both sexes this excretion rose with age until adolescence where it reached a plateau.In normal adults the men had significantly higher (p < 0.001) excretions of U-iPGF_2α than the women; also body weight and urinary creatinine excretion were higher in men (p < 0.001).In the children, as well as in the total population, U-iPGF_2α correlated best with body weight (r = 0.44 and r = 0.48 respectively; p < 0.001) and the urinary creatinine excretion (r = 0.53 and 0.57 respectively; p < 0.001); both body weight and urinary creatinine excretion are reflections of total body development. After the correction for urinary creatinine excretion or for body weight, the sex difference in the adult U-iPGF_2α totally disappeared.     

Renal NF-kappaB activation and TNF-alpha upregulation correlate with salt-sensitive hypertension in Dahl salt-sensitive rats

Molecular mechanisms of salt-sensitive (SS) hypertension related to renal inflammation have not been defined. We seek to determine whether a high-salt (HS) diet induces renal activation of NF-kappaB and upregulation of TNF-alpha related to the development of hypertension in Dahl SS rats. Six 8-wk-old male Dahl SS rats received a HS diet (4%), and six Dahl SS rats received a low-sodium diet (LS, 0.3%) for 5 wk. In the end, mean arterial pressure was determined in conscious rats by continuous monitoring through a catheter placed in the carotid artery. Mean arterial pressure was significantly higher in the HS than the LS group (177.9 +/- 3.7 vs. 109.4 +/- 2.9 mmHg, P < 0.001). There was a significant increase in urinary albumin secretion in the HS group compared with the LS group (22.3 +/- 2.6 vs. 6.1 +/- 0.7 mg/day; P < 0.001). Electrophoretic mobility shift assay demonstrated that the binding activity of NF-kappaB p65 proteins in the kidneys of Dahl SS rats was significantly increased by 53% in the HS group compared with the LS group (P = 0.007). ELISA indicated that renal protein levels of TNF-alpha, but not IL-6, interferon-gamma, and CCL28, were significantly higher in the HS than the LS group (2.3 +/- 0.8 vs. 0.7 +/- 0.2 pg/mg; P = 0.036). We demonstrated that plasma levels of TNF-alpha were significantly increased by fivefold in Dahl SS rats on a HS diet compared with a LS diet. Also, we found that increased physiologically relevant sodium concentration (10 mmol/l) directly stimulated NF-kappaB activation in cultured human renal proximal tubular epithelial cells. These findings support the hypothesis that activation of NF-kappaB and upregulation of TNF-alpha are the important renal mechanisms linking proinflammatory response to SS hypertension.     

Low sodium intake does not impair renal compensation of hypoxia-induced respiratory alkalosis.

Acute hypoxia causes hyperventilation and respiratory alkalosis, often combined with increased diuresis and sodium, potassium, and bicarbonate excretion. With a low sodium intake, the excretion of the anion bicarbonate may be limited by the lower excretion rate of the cation sodium through activated sodium-retaining mechanisms. This study investigates whether the short-term renal compensation of hypoxia-induced respiratory alkalosis is impaired by a low sodium intake. Nine conscious, tracheotomized dogs were studied twice either on a low-sodium (LS = 0.5 mmol sodium x kg body wt-1 x day-1) or high-sodium (HS = 7.5 mmol sodium x kg body wt-1 x day-1) diet. The dogs breathed spontaneously via a ventilator circuit during the experiments: first hour, normoxia (inspiratory oxygen fraction = 0.21); second to fourth hour, hypoxia (inspiratory oxygen fraction = 0.1). During hypoxia (arterial PO2 34.4 +/- 2.1 Torr), plasma pH increased from 7.37 +/- 0.01 to 7.48 +/- 0.01 (P < 0.05) because of hyperventilation (arterial PCO2 25.6 +/- 2.4 Torr). Urinary pH and urinary bicarbonate excretion increased irrespective of the sodium intake. Sodium excretion increased more during HS than during LS, whereas the increase in potassium excretion was comparable in both groups. Thus the quick onset of bicarbonate excretion within the first hour of hypoxia-induced respiratory alkalosis was not impaired by a low sodium intake. The increased sodium excretion during hypoxia seems to be combined with a decrease in plasma aldosterone and angiotensin II in LS as well as in HS dogs. Other factors, e.g., increased mean arterial blood pressure, minute ventilation, and renal blood flow, may have contributed.     

Relationship between exchangeable body sodium and urinary 6-keto-prostaglandin F1 alpha excretion in normal man

The renal prostaglandins are involved in the regulation of sodium balance. In the present study exchangeable body sodium (NaE) and the urinary excretion of the stable metabolite of prostacyclin, 6-keto-prostaglandin F1 alpha (6-k-PGF1 alpha) were determined simultaneously in 10 hospitalized healthy individuals. NaE was 1461 +/- 107 mmol/m2 body surface area, or 98.5 +/- 6.9% when expressed as percent of the normal value assessed on the basis of measurements in 54 control subjects. The excretion of 6-k-PGF1 alpha amounted to 68.3 +/- 39.2 ng/4 hr. Statistical evaluation revealed significant correlation between NaE and PGF1 alpha excretion (r = 0.642; p less than 0.05) and between the serum Na concentration and the urinary excretion of 6-k-PGF1 alpha (r = 0.865; p less than 0.001). The obtained results indicate that urinary 6-k-PGF1 alpha excretion, hence the renal synthesis of prostacyclin, are regulated, among other factors, by body sodium stores. The increased production of prostacyclin with expanding sodium space might be regarded as a compensatory response contributing to the renal elimination of excess sodium from the body. The signal to this response could be the serum Na concentration.     

Effect of estrogens on renal responsiveness to parathyroid hormone in elderly female subjects

The effect of estrogens on the renal responsiveness to parathyroid hormone (PTH) was examined by PTH loading tests with synthetic human-PTH (1-34) in 8 normal elderly females (mean +/- SD age, 81.0 +/- 7.1 yr) before and after administration of estrogen (Premarin 1.25 mg/day for 4 weeks). Basal urinary adenosine cyclic 3', 5'-monophosphate (cAMP) excretion showed a tendency to increase after estrogen administration (5.47 +/- 1.68 vs 6.60 +/- 2.67 nmol/100 ml GFR) and the theoretical renal phosphorous threshold showed a tendency to decrease from 3.22 +/- 0.98 to 2.73 +/- 0.56 mg/dl. The blood ionized calcium concentration did not change after estrogen administration (4.44 +/- 0.16 vs 4.32 +/- 0.20 mg/dl) and serum phosphorous (P) decreased significantly (3.65 +/- 0.47 vs 3.01 +/- 0.42 mg/dl, p less than 0.05). There was no increase in mean serum immunoreactive PTH (0.34 +/- 0.10 vs 0.34 +/- 0.05 ngeq/ml). The urinary excretions of cAMP in response to PTH loading [100 U of human-PTH (1-34), intravenously] significantly (p less than 0.05) increased (94.8 +/- 57.0 vs 196.7 +/- 118.3 nmol/100 ml GFR/h) after estrogen administration. Moreover the changes in urinary excretion of cAMP (r = 0.698, p less than 0.01) and P (r = 0.555, p less than 0.05) induced by the PTH loading were positively correlated with serum estradiol in elderly females, assessed as groups before and after estrogen administration. These results suggest that estrogens may enhance the renal responsiveness to exogenous PTH administration.     

Superoxide formation and interaction with nitric oxide modulate systemic arterial pressure and renal function in salt-depleted dogs

To determine the role of superoxide (O(2)(-)) formation in the kidney during alterations in the renin-angiotensin system, we evaluated responses to the intra-arterial infusion of an O(2)(-) - scavenging agent, tempol, in the denervated kidney of anesthetized salt-depleted (SD, n=6) dogs and salt-replete (SR, n=6) dogs. As expected, basal plasma renin activity was higher in SD than in SR dogs (8.4 +/- 1.0 vs. 2.3 +/- 0.6 ng angiotensin 1/ml/hr). Interestingly, the basal level of urinary F(2)-isoprostanes excretion (marker for endogenous O(2)(-) activity) relative to creatinine (Cr) excretion was also significantly higher in SD compared to SR dogs (9.1 +/- 2.8 vs. 1.6 +/- 0.4 ng F(2)-isoprostanes/mg of Cr). There was a significant increase in renal blood flow (4.3 +/- 0.5 to 4.9 +/- 0.6 ml/min/g) and decreases in renal vascular resistance (38.2 +/- 5.8 to 33.2 +/- 4.7 mm Hg/ml/min/g) and mean systemic arterial pressure (148 +/- 6 to 112 +/- 10 mm Hg) in SD dogs but not in SR dogs during infusion of tempol at 1 mg/kg/min for 30 mins. Glomerular filtration rate and urinary sodium excretion (U(Na)V) did not change significantly during tempol infusion in both groups of dogs. Administration of the nitric oxide synthase inhibitor nitro-L-arginine (50 mug/kg/min) during tempol infusion caused a reduction in U(Na)V in SR dogs (47% +/- 12%) but did not cause a decrease in SD dogs. These data show that low salt intake enhances O(2)(-) activity that influences renal and systemic hemodynamics and thus may contribute to the regulation of arterial pressure in the salt-restricted state.     

The source of urinary epidermal growth factor in humans

To clarify the source of human urine EGF, we studied EGF renal clearance in 20 healthy, young adult subjects. Immunoreactive EGF was measured hourly in EDTA plasma, heparin plasma, serum and urine of 12 males and 8 females during a 3 h study period. Plasma and urine creatinine and creatinine clearance were measured and calculated hourly. Mean (and SEM) creatinine clearance was similar in males and females (118 +/- 12 vs 105 +/- 6 ml/min). EGF was not detectable in plasma, whereas relatively high levels were measured in serum (2.5 +/- 0.25 vs 1.5 +/- 0.18 ng/ml in males and females respectively p less than 0.05). Urine EGF excretion averaged 1641 +/- 233 ng/h in males and 1507 +/- 191 ng/h in females (p greater than 0.05). A significant correlation was observed between urine creatinine and urine EGF concentrations in both male (r = 0.98, p less than 0.01) and female (r = 0.94, p less than 0.01) subjects. EGF immunoreactivity in urine and serum eluted from G-75 sephadex columns similarly to recombinant 6000 Mr hEGF. Urine excretion of EGF approximated 1.5 micrograms/h or 25 ng/mg creatine. The high concentrations of EGF found in urine in the face of non-detectable levels of EGF in plasma favor the hypothesis that EGF in urine is derived from kidney synthesis and secretion. The significant positive correlation between urine creatinine and urine EGF suggests a functional correlation between glomerular filtration and the process of tubular EGF excretion.     

Can serum amyloid A or macrophage colony stimulating factor serve as marker of amyloid formation process?

Amyloid formation depends on amyloid precursor production and is influenced by the activity of the underlying disorder and mediated by some proinflammatory cytokines. In this pilot study we tried to find some specific markers that could establish the activity of the disease. We investigated 45 samples of sera and 38 samples of urine from patients (pts) with secondary amyloidosis (AA), primary amyloidosis (AL), systemic autoimmune diseases with renal impairment (Vasc) and healthy controls (Co). Pts with AA had increased plasma levels of TNF alpha (9.97 +/- 4.22 vs. 2.63 +/- 1.34 pg/mL, p < 0.001) and SAA (43.14 +/- 16.0 vs. 3.42 +/- 0.7 ng/mL, p < 0.05) in comparison with Co. Plasma levels of M-CSF in the AA group were significantly increased in comparison with Co (1077.34 +/- 238.6 vs. 137.71 +/- 19.6, pg/mL, p < 0.001) and also in comparison with Vasc (482.24 +/- 86.7 pg/mL, p < 0.05). Urinary excretions of TNF alpha (8.92 +/- 8.1 vs. 0.17 +/- 0.11 microgram/mol creatinine, p < 0.01), sIL-6R (1.39 +/- 1.14 vs. 0.07 +/- 0.05 g/mol creatinine, p < 0.01) and M-CSF (650.2 +/- 153.7 vs. 33.3 +/- 8.6 micrograms/mol creatinine, p < 0.01) in AA were significantly increased in comparison with Co. Pts with AL had increased plasma levels of M-CSF (819.83 +/- 264.2 vs. 137.71 +/- 19.6 pg/mL, p < 0.05) and urinary excretion of M-CSF (865.0 +/- 188.4 vs. 33.3 +/- 8.6 micrograms/mol creatinine, p < 0.01) in comparison with Co. SAA has a low specificity for amyloidosis but is a sensitive acute phase reactant. TNF alpha, a proinflammatory cytokine, may reflect the activity of the underlying diseases in secondary amyloidosis. M-CSF was increased both in plasma and urine in amyloidosis groups and seems to be the most promising (possibly specific) marker of amyloidosis.     

Urinary excretion of glucagon-like peptide 1 (GLP-1) 7-36 amide in human type 2 (non-insulin-dependent) diabetes mellitus.

The urinary excretion of insulinotropic glucagon-like peptide 1 (GLP-1) was investigated as an indicator of renal tubular integrity in 10 healthy subjects and in 3 groups of type 2 diabetic patients with different degrees of urinary albumin excretion rate. No significant difference emerged between the groups with respect to age of the patients, known duration of diabetes, metabolic control, BMI, or residual beta-cell pancreatic function. Endogenous creatinine clearance was significantly reduced under conditions of overt diabetic nephropathy, compared with normo and microalbuminuric patients (p < 0.01). Urinary excretion of GLP-1 was significantly higher in normoalbuminuric patients compared to controls (490.4 +/- 211.5 vs. 275.5 +/- 132.1 pg/min; p < 0.05), with further increase under incipient diabetic nephropathy conditions (648.6 +/- 305 pg/min; p < 0.01). No significant difference resulted, in contrast, between macroproteinuric patients and non-diabetic subjects. Taking all patients examined into account, a significant positive relationship emerged between urinary GLP-1 and creatinine clearance (p = 0.004). In conclusion, an early tubular impairment in type 2 diabetes would occur before the onset of glomerular permeability alterations. The tubular dysfunction seems to evolve with the development of persistent microalbuminuria. Finally, the advanced tubular involvement, in terms of urinary GLP1 excretion, under overt diabetic nephropathy conditions would be masked by severe concomitant glomerular damage with the coexistence of both alterations resulting in a peptide excretion similar to control subjects.     

Urinary excretion of three nucleic acid oxidation adducts and isoprostane F(2)alpha measured by liquid chromatography-mass spectrometry in smokers, ex-smokers, and nonsmokers

To assess novel liquid chromatography/mass spectrometric methods for measuring oxidative damage to nucleic acids and lipids, we compared urinary excretion of 8-hydroxy-2'-deoxyguanosine (8-OHdG), 5-hydroxymethyl-2'-deoxyuridine (5-OHmU), and 8-hydroxyguanosine (8-OxoG), and an isoprostane, 8-iso-prostaglandin F(2)alpha (IsopF(2)alpha) in 234 healthy men (n = 113) and women (n = 121), 80 current smokers, 96 never-smokers), and 58 ex-smokers (no tobacco use for 3 years). The 8-OHdG and 8-OxoG did not differ significantly by group; 5-OHmU was higher in smokers, compared with ex- (p <.003) and never- (p <.0001) smokers and in ex- vs. never-smokers (p =.014) at, respectively, 13.5 +/- 0.7, 11.3 +/- 1.0, and 8.7 +/- 0.3 microg/g creatinine. IsopF(2)alpha was higher in smokers, compared with ex- (p =.007) and never-smokers (p <.0001) and in ex- vs. never- smokers (p =.002) at, respectively, 1.1 +/- 0.10; 0.74 +/- 0.07, and 0.51 +/- 0.04 microg/g creatinine. There were significant correlations among all three nucleic acid adducts and between IsopF(2)alpha and both 5-OHmU and 8-OHdG. Many smokers and ex-smokers had high levels of either 5-OHmU excretion or IsopF(2)alpha excretion, but not both. We conclude that 5-OHmU and IsopF(2)alpha are more discriminating of oxidative stress from tobacco smoke than the other two compounds measured. Whether characteristic patterns of excretion of these indicators forecast differential disease risk should be explored in future research.     

Urinary N tau-methylimidazole acetic acid excretion in respiratory disease

N tau-methylimidazole acetic acid (N tau-MIAA) is the principal urinary metabolite of histamine. The basal urinary excretion rate of N tau-MIAA was determined as 0.117 +/- 0.008 (SE) mg/h, with a renal clearance for N tau-MIAA of 273 +/- 27 ml/min implying active secretion. After subpharmacological infusion of histamine (50 ng.kg-1.min-1 over 2 h) in five volunteers that increased plasma histamine from 0.28 +/- 0.04 to 0.71 +/- 0.15 ng/ml, urinary excretion of N tau-MIAA over 8 h was increased by less than 17% compared with a control saline infusion. Urinary N tau-MIAA excretion in normal controls (273 +/- 14 micrograms/mmol creatinine) was similar to that observed in patients with severe acute asthma (253 +/- 22 micrograms/mmol), antigen-induced bronchoconstriction (269 +/- 21 micrograms/mmol), seasonal allergic rhinitis (304 +/- 31 micrograms/mmol), and clinically stable bronchiectasis (270 +/- 22 micrograms/mmol). In contrast, large increases in metabolite excretion (greater than 7,000 micrograms/mmol creatinine) were observed in a patient with systemic mastocytosis where very high plasma histamine levels were recorded (greater than 500 ng/ml) and marked systemic hemodynamic effects occurred. We conclude that urinary N tau-MIAA will only be increased in pathologies where sustained hyperhistaminemia occurs and that increased local histamine production in the lung or the upper airway does not cause a measurable change in the basal urinary excretion of this metabolite.     

Oxoproline kinetics and oxoproline urinary excretion during glycine- or sulfur amino acid-free diets in humans

L-5-oxoproline (L-5-OP) is an intermediate in glutathione synthesis, possibly limited by cysteine availability. Urinary 5-OP excretion has been proposed as a measure of glycine availability. We investigated whether 5 days of dietary sulfur amino acid (SAA-free) or glycine (Gly-free) restriction affects plasma kinetics of 5-OP and urinary excretion of L- and D-5-OP in 6 healthy men. On day 6, L-5-[1-(13)C]oxoproline and [3,3-(2)H(2)]cysteine were infused intravenously for 8 h (3 h fast/5 h fed). In a control study (adequate amino acid mixture), plasma oxoproline fluxes were 37.8 +/- 13.8 (SD) and 38.4 +/- 14.8 micromol x kg(-1) x h(-1); oxidation accounted for 85% of flux. Cysteine flux was 47.9 +/- 8.5 and 43.2 +/- 8.5 micromol x kg(-1) x h(-1) for fast and fed phases, respectively. Urinary excretion of L- and D-5-OP was 70 +/- 34 and 31.1 +/- 13.3 micromol/mmol creatinine, respectively, during days 3-5, and 46.4 +/- 13.9 and 22.4 +/- 8.3 micromol/mmol over the 8-h tracer study. The 5-OP flux for the Gly-free diet was higher (P = 0. 018) and tended to be higher for the SAA-free diet (P = 0.057) when compared with the control diet. Oxidation rates were higher on the Gly-free (P = 0.005) and SAA-free (P = 0.03) diets. Cysteine fluxes were lower on the the Gly-free (P = 0.01) and the SAA-free diets (P = 0.001) compared with the control diet. Rates of L-5-OP excretion were unchanged by withdrawal of SAA or Gly for 5 days but increased on day 6 (P = 0.005 and P = 0.019, respectively). Thus acute changes in the dietary availability of SAA and Gly alter oxoproline kinetics and urinary 5-OP excretion.     

Accurate quantification of dimethylamine (DMA) in human urine by gas chromatography-mass spectrometry as pentafluorobenzamide derivative: evaluation of the relationship between DMA and its precursor asymmetric dimethylarginine (ADMA) in health and disease

Dimethylamine [DMA, (CH(3))(2)NH)] is abundantly present in human urine. Main sources of urinary DMA have been reported to include trimethylamine N-oxide, a common food component, and asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthesis. ADMA is excreted in the urine in part unmetabolized and in part after hydrolysis to DMA by dimethylarginine dimethylaminohydrolase (DDAH). Here we describe a GC-MS method for the accurate and rapid quantification of DMA in human urine. The method involves use of (CD(3))(2)NH as internal standard, simultaneous derivatization with pentafluorobenzoyl chloride and extraction in toluene, and selected-ion monitoring of m/z 239 for DMA and m/z 245 for (CD(3))(2)NH in the electron ionization mode. GC-MS analysis of urine samples from 10 healthy volunteers revealed a DMA concentration of 264+/-173 microM equivalent to 10.1+/-1.64 micromol/mmol creatinine. GC-tandem MS analysis of the same urine samples revealed an ADMA concentration of 27.3+/-15.3 microM corresponding to 1.35+/-1.2 micromol/mmol creatinine. In these volunteers, a positive correlation (R=0.83919, P=0.0024) was found between urinary DMA and ADMA, with the DMA/ADMA molar ratio being 10.8+/-6.2. Elevated excretion rates of DMA (52.9+/-18.5 micromol/mmol creatinine) and ADMA (3.85+/-1.65 micromol/mmol creatinine) were found by the method in 49 patients suffering from coronary artery disease, with the DMA/ADMA molar ratio also being elevated (16.8+/-12.8). In 12 patients suffering from end-stage liver disease, excretion rates of DMA (47.8+/-19.7 micromol/mmol creatinine) and ADMA (5.6+/-1.5 micromol/mmol creatinine) were found to be elevated, with the DMA/ADMA molar ratio (9.17+/-4.2) being insignificantly lower (P=0.46). Between urinary DMA and ADMA there was a positive correlation (R=0.6655, P<0.0001) in coronary artery disease, but no correlation (R=0.27339) was found in end-stage liver disease.