Molecular size distribution of immunoreactive trypsin and renal tubular dysfunction: role in trypsin plasma-urine transfer

In order to investigate the role of circulating free trypsinogen and renal tubular dysfunction in affecting trypsin plasma-urine transfer, serum immunoreactive trypsin (IRT), its urinary output, IRT molecular size distribution, filtrable immunoreactive trypsin, gamma-glutamyltransferase and alpha-glucosidase outputs were studied in 6 control subjects, 9 patients with pancreatic cancer and 15 with chronic pancreatitis. The majority of immunoreactivity was always eluted at a molecular weight of about 24,000 and might therefore be considered as free trypsinogen. Variable amounts of IRT at higher molecular weights, possibly represented by trypsin-inhibitor complexes, were also detected. Increasing IRT levels were generally accounted for by free trypsinogen, regardless of the nature of the disease. Unlike serum free trypsinogen levels, renal tubular damage, evaluated by means of the excretion of two high-molecular weight urinary enzymes, seems to play a prominent role in explaining trypsin plasma-urine transfer.     

Renal handling of amylase and immunoreactive trypsin in pancreatic cancer and chronic pancreatitis.

In order to evaluate the renal metabolism of amylase and immunoreactive trypsin (IRT) in chronic pancreatic disease, we assayed amylase, IRT and creatinine in serum and urine and gamma-glutamyl transferase (GGT) in dialyzed urine as well as alpha-glucosidase (AGL) and ribonuclease (RNase) in 24 control subjects, 34 patients with pancreatic cancer, 52 with chronic pancreatitis and 32 with extra-pancreatic diseases. Urinary amylase and IRT outputs were found to be more elevated in chronic pancreatitis than in control subjects. The levels of serum amylase, its renal inputs and outputs were correlated with the corresponding IRT values. Multiple regression analyses (dependent on amylase or IRT urinary outputs, circulating levels of the two enzymes, creatinine clearance and the excretion of GGT, AGL and RNase predictor variables) showed significant correlations. The standardized partial regression coefficients found to be significant were: GGT, RNase and serum amylase for amylase, and GGT and RNase for IRT. No difference was found between amylase and IRT outputs in patients with chronic pancreatitis, taking the presence or the absence of alcohol abuse, exocrine insufficiency and pancreatic pseudocysts into consideration. Urinary GGT excretion correlated with serum amylase and IRT levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serum elastase 1 and immunoreactive trypsin in chronic pancreatic disease: is there any relationship with trypsin inhibitors?

In order to investigate modifications of serum levels of elastase 1, immunoreactive trypsin, alpha 1-antitrypsin and alpha 2-macroglobulin in chronic pancreatic disease, and to speculate on the possible relationships among these parameters, the enzymes and inhibitors were assayed in the sera of 33 control subjects, 34 pancreatic cancer, 28 chronic pancreatitis and 36 extra-pancreatic diseases. An increase of elastase 1, alpha 1-antitrypsin and alpha 2-macroglobulin was detected in pancreatic cancer, chronic pancreatitis and extra-pancreatic diseases; no changes were found for serum immunoreactive trypsin. Multiple regression analyses showed that only 7% of elastase 1 was explained by inhibitors with alpha 1-antitrypsin playing a major role. Inhibitors did not influence immunoreactive trypsin. Our data indicate that the variations of the serum levels of proteases and antiproteases in chronic pancreatic disease are probably independent of each other.     

Renal function in transgenic rats expressing an angiotensin-(1-7)-producing fusion protein

Transgenic rats [TGR(A1-7)3292] present a chronic 2.5-fold increase in plasma Angiotensin-(1-7) [Ang-(1-7)] concentration. In the present study, we investigated the effects of this chronic elevation on renal function, vasopressin levels, kidney morphology, expression of Ang-(1-7) and vasopressin receptors in TGR(A1-7)3292. Urine volume and water intake were measured for 24 h. At the end of this period, plasma and urine samples were collected to evaluate renal function parameters and circulating vasopressin levels. Expression of renal V2 receptors and Mas was assessed by ribonuclease protection assay. Renal slices were processed for histological analysis. The urine flow of TGR(A1-7)3292 was significantly lower in comparison with Sprague-Dawley rats. The reduced urine volume of TGR(A1-7)3292 was accompanied by a significant increase in urinary osmolality and decrease free water clearance. Glomerular filtration rate, urinary sodium and potassium excretion were similar in both strains. No significant changes were observed in vasopressin levels as well as in V2 receptor and Mas mRNA expression in renal tissue. No changes in kidney structure of TGR(A1-7)3292 were detected. These data suggest that changes in circulating renin-angiotensin system produced by chronic increase of Ang-(1-7) levels can lead to adjustments in the water balance that are independent of vasopressin release and V2 receptor expression.     

Tamm-Horsfall protein regulates circulating and renal cytokines by affecting glomerular filtration rate and acting as a urinary cytokine trap

Although few organ systems play a more important role than the kidneys in cytokine catabolism, the mechanism(s) regulating this pivotal physiological function and how its deficiency affects systemic cytokine homeostasis remain unclear. Here we show that elimination of Tamm-Horsfall protein (THP) expression from mouse kidneys caused a marked elevation of circulating IFN-γ, IL1α, TNF-α, IL6, CXCL1, and IL13. Accompanying this were enlarged spleens with prominent white-pulp macrophage infiltration. Lipopolysaccharide (LPS) exacerbated the increase of serum cytokines without a corresponding increase in their urinary excretion in THP knock-out (KO) mice. This, along with the rise of serum cystatin C and the reduced inulin and creatinine clearance from the circulation, suggested that diminished glomerular filtration may contribute to reduced cytokine clearance in THP KO mice both at the baseline and under stress. Unlike wild-type mice where renal and urinary cytokines formed specific in vivo complexes with THP, this "trapping" effect was absent in THP KO mice, thus explaining why cytokine signaling pathways were activated in renal epithelial cells in such mice. Our study provides new evidence implicating an important role of THP in influencing cytokine clearance and acting as a decoy receptor for urinary cytokines. Based on these and other data, we present a unifying model that underscores the role of THP as a major regulator of renal and systemic immunity.     

Plasma endothelin-1 levels and albumin excretion rate in normotensive,microalbuminuric type 2 diabetic patients

BACKGROUND: Endothelin-1 (ET-1) is able to determine functional and structural renal alterations and plasma levels of this vasoconstrictor peptide are increased in diabetic patients. In a selected group of type 2 normotensive diabetic patients with microalbuminuria, we investigated circulating ET-1 levels compared to a control group and verified whether there is a relationship between ET-1 levels and albumin excretion rate in diabetics. SUBJECTS AND METHODS: Thirty-two microalbuminuric type 2 diabetic patients (12 males and 20 females; mean age 57 +/- 8 years) without hypertension, renal failure, hypercholesterolemia or atherosclerotic damage were selected. The control group was made up of 28 healthy subjects matched for sex and age. Blood pressure, creatinine clearance, serum cholesterol and plasma ET-1 values were determined in diabetic and control group. In diabetic patients, glycosilated hemoglobin and urinary albumin excretion rate were also assayed. Mean ET-1 values in diabetics and controls were compared using Student's t-test. Linear regression test was done to relate two variables. Statistical significance was set at p<0.05. RESULTS: Mean ET-1 values were significantly higher in the diabetic group than in controls (11.77 +/- 1.16 pg/ml vs 8.9 +/- 2.1 pg/ml; p<0.05). No relationship (p>0.05) was found between circulating ET-1 and blood pressure, creatinine clearance, serum cholesterol and metabolic control in diabetics. There was a significant positive correlation (r=0.403; p=0.03) between plasma ET-1 levels and albumin excretion rate in diabetic patients. CONCLUSIONS: Our results showed that circulating ET-1 values were increased in microalbuminuric, normotensive, type 2 diabetic patients and correlated with albumin excretion rate. These findings confirm that endothelial dysfunction, as expressed by ET-1 levels, occurs early in these patients and support the hypothesis of a potential role for this peptide in development of microalbuminuria in diabetic nephropathy.     

Clinical value of serum immunoreactive trypsin concentration.

The clinical value of estimation of serum concentrations of immunoreactive trypsin was evaluated by studying 46 healthy controls, 23 controls in hospital, 44 patients with chronic pancreatic disease, and 184 patients with non-pancreatic conditions in which pancreatic disease commonly enters into the differential diagnosis. Serum trypsin concentration had a log normal distribution in the controls, and the calculated normal range was considerably wider than that previously reported. The concentration was abnormal in only 13 out of 27 patients with chronic pancreatitis and was extremely variable in patients with pancreatic cancer. Abnormal results occurred in 11% of the patients with non-pancreatic disease. Eighteen patients had a subnormal trypsin concentration, of whom six did not have pancreatic disease and 12 had either chronic pancreatitis or pancreatic cancer. There was no correlation between serum trypsin concentration and mean tryptic activity as measured by the Lundh test. Of 11 patients with pancreatic steatorrhoea, only seven had subnormal trypsin concentrations. There results suggest that the serum concentrations of immunoreactive trypsin has a low specificity and sensitivity for pancreatic disease and does no reflect the degree exocrine insufficiency in patients with proved chronic pancreatitis.     

Measurement of thyroid stimulating hormone (TSH) in human urine

Using a highly sensitive and specific immunoradiometric assay kit for human TSH, we measured TSH concentrations in unprocessed urines in normal subjects, in patients with primary hypothyroidism, and patients with renal disease. In five of ten normal subjects TSH was detectable in urine samples (less than 20-69 microU/day). In five patients with hypothyroidism, the urinary TSH excretion was increased. In seven out of ten patients with nephrotic syndrome, eight out of nine patients with chronic renal failure and two patients with tubular dysfunction, the urinary TSH excretion was increased. The urinary TSH excretion correlated significantly with both urinary protein excretion and urinary beta 2-microglobulin excretion. These results suggest that the renal handling of TSH involves both glomerular filtration and tubular re-absorption, and that urinary TSH excretion is increased when serum TSH is increased and either glomerular or tubular function is impaired.     

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.     

Serum, urinary, and salivary nitric oxide in rheumatoid arthritis: complexities of interpreting nitric oxide measures

Nitric oxide (NO) may play important roles in rheumatoid arthritis (RA). RA is an inflammatory disease involving joints and other systems including salivary glands. To assess NO production in RA patients, we compared levels of serum, urine, and salivary nitrite and nitrate (NOx) in patients with RA and normal subjects, and we examined the relationships of these measures to disease activity. Serum, urine, and NOx levels as well as renal creatinine, NOx clearance and fractional excretion rates were compared in 25 RA patients and 20 age- and gender-matched healthy controls. Subjects were hospitalized for 3 days and placed on a NOxrestricted diet. NOx was assayed using nitrate reductase and the Griess reagent. RA activity was assessed using standard clinical and laboratory measures. While consuming a restricted diet for 3 days to eliminate the effects of oral intake of NOx, 24 hour urinary NOx excretion decreased in both RA patients and healthy controls. Urine NOx levels at all time points were not significantly different between RA patients and normal subjects. Serum NOx levels also decreased during the 3 days of NOx restriction, but RA patients had higher serum NOx levels at all time points compared with the control group. Likewise, serum NOx/creatinine ratios were higher in RA patients than in controls. Although basal salivary flow rate and tear flow were lower in RA patients, salivary NOx levels did not differ between normal and RA subjects. While renal creatinine clearance was not different between the two groups, we found that RA patients had lower renal NOx clearance and lower renal NOx fractional excretion. After correction of p values for multiple comparisons, there were no significant relationships for the RA group between measures of disease activity and the urinary NOx, serum NOx, or urinary NOx clearance. Despite interest in the use of NO as a marker of disease activity, alterations in renal NOx clearance and fractional excretion in RA make it difficult to assess in vivo NO production even with strict dietary restriction of NOx intake.     

Renal excretion of fluoride in renal failure and after renal transplantation.

We have compared the renal excretion of fluoride in a variety of patients with chronic renal failure maintained with and without protein restriction before and during regular dialysis treatment and after transplantation. The patients tended to continue to excrete normal dietary loads of fluoride quite well until renal function was seriously reduced. From a regression of function on excretion the mean level of creatinine clearance when a normal dietary load of fluoride 0.0526 plus or minus 0.019 mmol/2 h (1.0 plus or minus 0.36 mg/24h) has a 90% chance of being excreted lies around 16 ml/min, a level when most patients with renal failure will be symptomatic. Acute loading of such patients with additional fluoride in the form of sodium fluoride from 40 mg to 60 mg/day showed a twofold to threefold increase of serum fluoride concentrations, slight increases in urinary fluoride excretion, and heavy tissue absorption, suggesting that prior fluoride loading of the skeleton had not taken place. These effects contrasted with those in one patient with normal renal function and with those in one patient with skeletal saturation due to prolonged loading. After renal transplantation fluoride excretion increased but reached normal levels within three months of satisfactory function, suggesting that fluoride loading in renal failure and during regular dialysis therapy had not been excessive.     

Familial hypocalciuric hypercalcaemia and acute pancreatitis.

Four families with familial hypocalciuric hypercalcaemia were studied. The probands presented with abdominal pain, which in three was due to acute pancreatitis; in two the condition was life threatening. Serum concentrations of calcium, magnesium, phosphate, and immunoassayable parathyroid hormone, urinary calcium excretion, and the rate of renal tubular reabsorption of phosphate were measured; the findings were compared with results in 10 patients with primary hyperparathyroidism matched for serum calcium concentration to establish differences between the diseases. Familial hypocalciuric hypercalcaemia should be suspected in patients with hypercalcaemia in whom daily urinary calcium excretion is below 5 mmol (200 mg) provided renal insufficiency, vitamin D deficiency, and ingestion of drugs that reduce calcium excretion have been excluded. Most cases appear to run a benign course, but some may suffer considerable morbidity. Surgical treatment should be reserved for patients with severe complications, when all parathyroid tissue should be removed.     

Gamma-glutamyltransferase release by the post ischemic kidney: multiple forms and cellular pH

The release of gamma-glutamyltransferase from renal tubule cells was studied in situ following 30 minutes of ischemia. The ischemic kidney enzyme level fell 33 percent after 15 minutes of reflow of which only 1.2 percent was recovered in the urine; none was released into the renal vein. At this time the overwhelming majority of the enzyme appears bound to membranes in both the kidney and the urine. In the subsequent 15 minutes renal levels continue to decline while urinary excretion accounts for 5 percent of that disappearing from the kidney. Interestingly the form of the enzyme present in kidney and urine shifts to a soluble form coinciding with cellular alkalosis, urinary alkalinization and a rise in ATP levels. Alkalinization of renal homogenates result in a 2-fold increase in the soluble enzyme form. The results are consonant with the immediate loss of brush border enzyme via uptake into the cell or release into the urine with the former pathway predominating; subsequent appearance of the soluble enzyme appears to reflect intracellular alkaline proteinase activity and exocytosis. The form in which the enzyme is excreted may provide a useful clinical index: membranous reflecting cellular necrosis and soluble reflecting cellular recovery.     

Renal handling of zinc in insulin-dependent diabetes mellitus patients

Hyperzincuria is a common feature in diabetic patients, which is still not understood. Based on the above consideration, the aim of the present study was to investigate the renal handling of zinc in insulin-dependent diabetes mellitus (IDDM) patients. The glomerular filtration rate, urinary zinc excretion, zinc clearance, zinc clearance/creatinine clearance ratio, zinc tubular reabsorption, glycosuria, plasma glucose, C-peptide, glucagon, and cortisol were investigated in 10 normal individuals (Group C1 and Group C2, respectively) and 10 IDDM patients (Group E1: hyperglycemic and glycosuric and Group E2: normoglycemic and aglycosuric) during placebo or venous zinc tolerance test. The results showed that urinary zinc excretion and renal zinc clearance were increased after zinc injection in normal individuals (Group C2) and IDDM patients (Groups E1 and E2) when compared with normal individuals-placebo (Group C1). However, these renal parameters were statistically more significant in the hyperglycemic and glycosuric diabetics (Group E1). Because patients in Group E1 had the lowest plasma C-peptide levels and showed a strong negative correlation between CZn⁺⁺/Ccr ratio and this hormone, we suggest that in this setting insulin inhibits urinary zinc excretion.     

垂体在刺激脑内渗透压感受器引起的肾脏反应中的作用

实验在α氯醛糖和氨基甲酸乙酯混合麻醉的大鼠中进行。脑室内注射高张盐水(icv.HS)后,肾血浆流量、肾小球滤过率、尿量、尿钠排出量、尿钾排出量和渗透物质清除率均增加,游离水清除率下降。去除垂体后,icv.HS不再能引起上述肾脏反应。另外给大鼠静脉注射血管升压素(VP)拮抗剂(V_1和V_2受体拮抗剂),并不能削弱上述icv.HS引起的肾脏反应。脑室内注射高张盐水后,尿中多巴胺(DA)排出量无显著增多;给予多巴脱羧酶抑制剂苄丝肼也不能削弱icv.HS引起的肾脏反应。上述实验结果表明,在本实验条件下刺激脑内渗透压感受器引起的肾脏反应依赖于垂体的完整性,但看来并不依赖于外周的VP和DA,故垂体通过何种机制介导icv.HS引起上述肾脏反应,有待于进一步的研究。     

Tritium labeling of thermolysin, elastase, and ribonuclease by exposure to tritium gas at low pressure

The bacterial metalloendoprotease thermolysin, bovine pancreatic ribonuclease, and porcine pancreatic elastase have been tritiated by exposure to subcurie amounts of tritium gas at pressures below 50 mTorr for periods of 1 to 6 h. Thermolysin, ribonuclease, and elastase have been purified to specific radioactivities of 15, 5, and 1 Ci/mol, respectively. Amino acid analyses of the tritiated enzymes revealed higher relative specific radioactivities for His, Pro, and Phe in all three proteins while Val and Ile were among the residues with the lowest relative specific radioactivities. The recovery of enzyme activity was always greater than 95% and the formation of tritiated decomposition products was not observed. This lowpressure gas exposure process requires less tritium gas and less time than the original method of Wilzbach to achieve equal or higher levels of tritium incorporation. In addition, the enzymes were completely active and did not show the presence of highly radioactive byproducts which have been observed in earlier studies of the Wilzbach labeling of proteins.     

Increased serum levels of basic fibroblast growth factor in patients with renal cell carcinoma.

The serum level and urinary output of basic and acidic fibroblast growth factors (FGFs) were measured by sandwich enzyme immunoassay (EIA) in patients with renal cell carcinoma. In over fifty percent (16/31) of renal cell carcinoma patients, basic FGF was elevated (greater than 30 pg/ml) in their sera. There is relatively good correlation between serum levels of basic FGF and tumor stage or grade, while urinary daily output of basic FGF did not correlate with increased malignancy. The present results indicate that serum basic FGF level of patients with renal cell carcinoma is a useful diagnostic and prognostic marker for renal cell carcinoma. On the other hand, acidic FGF was not detectable in all sera and urine.     

Human ribonucleases. Quantitation of pancreatic-like enzymes in serum, urine, and organ preparations

Antibodies against pure human pancreatic ribonuclease (RNase) were used to study ribonuclease levels in human tissues and body fluids. The antibodies completely inhibit the activity of purified RNase as well as ribonuclease activity in crude pancreatic extracts. RNase activity is inhibited by 70-80% in serum and urine, indicating that a significant proportion of the RNases in these preparations are structurally like the pancreatic enzyme. In contrast, inhibition of RNase activities from spleen (8%) and liver (30%) was inefficient suggesting that most of the RNases in these tissues are structurally unlike the pancreatic enzyme. A competitive binding radioimmunoassay (RIA), sensitive in the range of 1-100 ng of RNase, was developed to quantitate the pancreatic like enzymes. The RIA of crude tissue preparations and samples fractionated by gel filtration was compatible with inhibition results. Enzymes structurally like pancreatic RNase could be quantitated despite the presence of other RNase activities. Immunological quantitation of pancreatic like RNases was also found to be much more simple and precise than enzymatic assays comparing RNA and polycytidylate substrates. We suggest the immunological assays will be useful in the quantitation and definition of tissue of origin of RNases in serum of patients with pancreatic carcinoma.     

Ribonuclease in the experimental therapy of pancreatitis

The influence of ribonuclease on the morphogenesis of experimental pancreatitis in the albino rats has been studied. The drug injected during edematous stage of pancreatitis caused some decrease of pancreatic enzymes level in the blood at hemorrhagic stage and its normalization at necrotic stage of pancreatitis. The development of hemorrhagic and necrotic stages of pancreatitis did not change under the influence of ribonuclease. The maturation of connective tissue of pseudocyst capsule was delayed and inflammatory infiltration of necrotic tissues and their elimination were increased under the influence of the drug. There were extensive tubular transformations of acini and early fibrosis and lipomatosis in the frontier zone. In the viable parts of pancreas moderate hypertrophy of exocrine pancreatocytes developed and chronic pancreatitis features appeared with use of ribonuclease.     

The low nanomolar levels of N<Superscript>G</Superscript>-monomethylarginine in serum and urine of patients with chronic renal insufficiency are not significantly different from control levels

Summary.  There are no reliable mean values of N^G-monomethylarginine (NMMA) in blood and urine of patients with renal insufficiency available in the literature. Therefore we investigate whether the NMMA levels are changed in blood and urinary excretion of nondialysed and dialysed patients with chronic renal insufficiency to evaluate whether NMMA may reach sufficiently increased concentrations in blood of the patients to exert toxic biological activity. In nondialysed as well as in dialysed patients we find no significant difference in serum concentration of NMMA between patients and controls. In nondialysed patients (all with a residual creatinine clearance lower than 15 ml/min), we find 94.5 ± 26.1 nM (mean ± SD) versus 94.6 ± 19.5 nM in controls. Similar levels are found in serum of haemodialysed patients (each with serum creatinine levels >700 μM): 83.0 ± 20.2 nM. The urinary excretion of NMMA in nondialysed patients is also not significantly different from the excretion of controls: 123 ± 110 in patients versus 157 ± 117 nmol/24 hrs in controls. Furthermore, the clearance of NMMA is much lower compared to the clearance of the dimethylarginine derivatives. Based on the literature, the low nanomolar levels of NMMA found in blood of patients with renal insufficiency do not support the statement that NMMA proper may act as a uremic toxin. Received April 3, 2002 Accepted October 7, 2002 Published online January 20, 2003 Acknowledgements We thank the University of Antwerp, FWO (Fonds voor Wetenschappelijk Onderzoek) (G.0027.97 and G.0394.00), the Born-Bunge Foundation, the OCMW Medical Research Foundation and Neurosearch Antwerp for the financial support. Authors' address: Bart Marescau, Laboratory of Neurochemistry and Behaviour, UIA T504, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Belgium, Fax: 00 32 3 8202618; E-mail: bartold.marescau@ua.ac.be