Urinary excretion of proteins among metal welders

Joining of metals by welding confer an exposure of dust particulates containing several toxic substances. Chromium, nickel and manganese is absorbed in the lungs and may adversely affect the renal function. We compared biological markers of glomerular filtration (Kampmann clearance) and tubular function (post-shift urine spot sample concentration of respectively albumin, immunoglobulin G, transferrin, orosomucoid and beta 2-microglobulin) among 102 ever-welders and 33 never-welders (mostly electricians). The welders were subdivided into groups of stainless steel welders (n = 35), mild steel welders (n = 46) and ex-welders (n = 21). Each group was separately referenced with never-welders. The Kampmann clearance was within normal limits in all workers and not related to welding exposure. However, the urinary concentration of the majority of proteins was 1.5 to 3.0 times higher in both stainless steel and mild steel welders. The number of welding years taken as a measure of cumulative welding exposure was not related to levels of proteins in urine when adjusting for the effect of age. In addition, no alteration of urinary proteins was found among the ex-welders apart from slightly elevated albumin. This indicates that the apparent effect of welding on renal tubular function may at least partially be reversible. In conclusion, this study is in support of the hypothesis that metal welding may adversely affect renal tubular function, but it is questionable whether welding exposure has bearings as to occurrence of clinical significant kidney disease.

[Clinical significance of changing from a second to a third generation thyroid stimulating hormone (TSH) assay]

In recent years new sensitive immunochemoluminiscentic methods to measure thyroid stimulating hormone, TSH have been introduced. In this investigation we have made a comparison between an older, less sensitive, second generation TSH assay and a new, sensitive, third generation TSH assay in order to evaluate if new information of clinical value is obtained. We found that 20% of all the sera that were sent to the laboratory for TSH measurement showed low values. In the sera with low TSH concentration a great variation was observed between the "correct" values found with the third generation assay and the values found with the less sensitive second generation assay. We conclude, that since many sera sent to a routine laboratory have low TSH concentrations, and since it is of clinical importance to know the correct TSH value in many different patient categories, a third generation TSH assay is recommended in the daily routine.

Sensitive enzyme-linked immunosorbent assay for measurement of autoantibodies to human thyroid peroxidase

The development of a sensitive assay for detection of autoantibodies against one of the major thyroid antigens, thyroid peroxidase (TPO), is described. TPO was purified from human thyroid tissue by: (1) isolation of thyroid microsomes using homogenization and differential centrifugation, (2) solubilization of membrane proteins by Zwittergent 3-14, and (3) anion exchange liquid chromatography on a FPLC Mono Q column. Autoantibodies against TPO (TPO-Ab) were measured using an enzyme-linked immunosorbent assay (ELISA) with serum samples diluted 1:100. Standards containing 70, 7, 0.7, 0.02 and 0 U ml-1 TPO-Ab were employed (reference standard code 66/387 NIBSC, London, UK). The detection limit was 0.02 U ml-1 corresponding to 2 U ml-1 in undiluted serum. The inter- and intra-assay coefficients of variation were 8.6% and 5.3%. In 109 healthy control subjects TPO-Ab was found in 9 (8.3%), while 43 (97.7%) out of 44 patients with newly diagnosed untreated Graves' disease had detectable TPO-Ab in serum. All of 16 patients with newly diagnosed spontaneously developing primary hypothyroidism had circulating TPO-Ab (range 16-7000 U ml-1). The new assay is a valuable tool for evaluation of thyroid autoimmunity in individual patients and for studying the epidemiology of thyroid autoimmunity.

Preanalytical handling of stored urine samples, and measurement of beta 2-microglobulin, orosomucoid, albumin, transferrin and immunoglobulin G in urine by enzyme-linked immunosorbent assays (ELISA)

Urinary beta 2-microglobulin, orosomucoid, albumin, transferrin and IgG were measured by enzyme-linked immunosorbent assays (ELISA). In urine samples stored at -20 degrees C three of these proteins decreased during the period of freezing. After 1 week at -20 degrees C urinary transferrin decreased by 81%, IgG by 39% and albumin by 26% of the pre-freezing values; however, addition of Tween-20 restored these values. In previously stored urine samples with bovine albumin, the decreased value after freezing at -20 degrees C could be increased by changing the thawing procedure and including addition of Tween-20. Urine samples thawed at room temperature just before analysis decreased by 80% for transferrin, 57% for IgG, 30% for albumin and 26% for beta 2-microglobulin compared with samples thawed at 37 degrees C, had Tween-20 added and then were kept for a few days at room temperature before analysis. Furthermore, previously frozen urine samples that were thawed at 37 degrees C, had Tween-20 added and then were stored at room temperature did not show significant changes in any of the protein results measured the day after thawing and 35 days later. Orosomucoid seemed to be less variable as regards the effect of freezing and thawing procedure.

The stages in diabetic renal disease. With emphasis on the stage of incipient diabetic nephropathy

Alterations in renal function and structure are found even at the onset of diabetes mellitus. Studies performed over the last decade now allow definition of a series of stages in the development of renal changes in diabetes. Such a classification may be useful both in clinical work and in research activities. Stage 1 is characterized by early hyperfunction and hypertrophy. These changes are found at diagnosis, before insulin treatment. Increased urinary albumin excretion, aggravated during physical exercise, is also a characteristic finding. Changes are at least partly reversible by insulin treatment. Stage 2 develops silently over many years and is characterized by morphologic lesions without signs of clinical disease. However, kidney function tests and morphometry on biopsy specimens reveal changes. The function is characterized by increased GFR. During good diabetes control, albumin excretion is normal; however, physical exercise unmasks changes in albuminuria not demonstrable in the resting situation. During poor diabetes control albumin excretion goes up both at rest and during exercise. A number of patients continue in stage 2 throughout their lives. Stage 3, incipient diabetic nephropathy, is the forerunner of overt diabetic nephropathy. Its main manifestation is abnormally elevated urinary albumin excretion, as measured by radioimmunoassay. A level higher than the values found in normal subjects but lower than in clinical disease is the main characteristic of this stage, which appeared to be between 15 and 300 micrograms/min in the baseline situation. A slow, gradual increase over the years is a prominent feature in this very decisive phase of renal disease in diabetes when blood pressure is rising. The increased rate in albumin excretion is higher in patients with increased blood pressure. GFR is still supranormal and antihypertensive treatment in this phase is under investigation, using the physical exercise test. Stage 4 is overt diabetic nephropathy, the classic entity characterized by persistent proteinuria (greater than 0.5 g/24 h). When the associated high blood pressure is left untreated, renal function (GFR) declines, the mean fall rate being around 1 ml/min/mo. Long-term antihypertensive treatment reduces the fall rate by about 60% and thus postpones uremia considerably. Stage 5 is end-stage renal failure with uremia due to diabetic nephropathy. As many as 25% of the population presently entering the end-stage renal failure programs in the United States are diabetic. Diabetic nephropathy and diabetic vasculopathy constitute a major medical problem in society today.

Albumin excretion and renal haemodynamic response to physical exercise in normal and diabetic man

The relationship between exercise albuminuria and changes in renal haemodynamics during exercise in diabetes was investigated. In thirteen male, juvenile diabetic patients and seven comparable normal subjects GFR (125 I-iothalamate clearance) and RPF (131 I-hippuran clearance) as well as urinary albumin excretion were measured during the exercise test (450 kpm/min followed by 600 kpm/ min each for 20 min). All examined persons had normal baseline albumin excretion. The diabetics with a diabetes duration of 3-17 years exhibited increased albumin excretion during exercise, whereas there was no difference between the normals and the diabetics with less than 2 years of diabetes duration. The percentage changes during exercise in GFR, RPF and filtration fraction (FF) were at the same level in diabetics and normals. The FF was higher both in baseline values and during exercise for the two groups of diabetics when compared to the normals but no correlation between FF and albumin excretion could be demonstrated. Thus, elevated FF alone per se does not induce increase in albumin excretion. Systemic haemodynamics, heart rater and blood pressure, showed no difference between any of the groups. Concerning the abnormal albumin response in diabetics, it is concluded that the most likely explanation is that the glomerular membrane in these patients is unable to retain albumin when increased filtration pressure is operating during exercise. Altered renal haemodynamics during exercise may play a contributory role.

Acute effects of insulin on plasma noradrenaline and the cardiovascular system

It is now known that insulin has marked acute effects on plasma noradrenaline and the cardiovascular system. These effects of insulin are not due to hypoglycemia and occur without changes in plasma adrenaline. Intravenous injection of insulin in juvenile diabetics increased plasma noradrenaline and heart rate and decreased glomerular filtration rate, renal and peripheral blood flow, and plasma volume. Urinary excretion rates of beta-2-microglobulin and urinary volume decreased after insulin, whereas urinary albumin excretion increased. When blood glucose was maintained by glucose infusion after insulin, glomerular filtration rate and renal blood flow remained unaltered whereas plasma noradrenaline, heart rate, and urinary albumin excretion increased and beta-2-microglobulin excretion decreased. Decreases in glomerular filtration rate and renal blood flow after insulin are thus due to the fall in blood glucose. Rise in albumin excretion after insulin is probably of glomerular origin and not caused by the fall in blood glucose or by changes in renal hemodynamics. In patients with long-term diabetic nephropathy and albuminuria, insulin decreased albumin excretion (probably due to renal vasoconstriction) and plasma noradrenaline did not increase. In alloxan-diabetic rabbits the increase in heart rate after insulin was not abolished by autonomic blockade. In short-term streptozotocin-diabetic rats, muscle capillary endothelial cells showed a reduced number of free micropinocytotic vesicles. The number was nearly normalized 1 hr after intramuscular injection of insulin. The mechanism of action of insulin on plasma noradrenaline, heart rate, plasma volume, and urinary albumin excretion is not known. The rise in plasma noradrenaline after insulin may be compensatory to hypovolemia or to antagonizing effects of insulin on some actions of noradrenaline. The findings in streptozotocin-diabetic rats suggest that insulin may be essential for the normal function of capillary endothelial cells.

Intravenous insulin decreases urinary albumin excretion in long-term diabetics with nephropathy

The effect of intravenous injection of insulin on heart rate, plasma noradrenaline and urinary excretion rates of albumin and beta-2-microglobulin was examined in 10 long-term diabetics, 5 of whom had albuminuria. --In patients without albuminuria intravenous injection of insulin resulted in changes similar to but less pronounced than those previously observed in short-term diabetics: albumin excretion, plasma noradrenaline and heart rate increased, creatinine excretion decreased significantly. --Intravenous injection of insulin increased heart rate but not plasma noradrenaline in long-term diabetics with albuminuria. Arterial blood pressure did not change after insulin. Contrary to expectation insulin decreased urinary albumin excretion (from 418 to 312 micrograms/min, 27 per cent) in these patients. There was a marked decrease in urinary excretion rates of beta-2-microglobulin and creatinine (55 and 17 per cent, respectively) after insulin. --The decrease in albumin excretion after insulin in diabetics with albuminuria is most likely due to renal vasoconstriction. The absence of a rise in albumin excretion after insulin may be due to severe morphological changes in glomeruli in these patients.

The renal handling of amylase in normal man

The renal glomerular and tubular transport rate of amylase was studied by measuring the urinary excretion of this protein before and during inhibition of tubular protein reabsorption by lysine. The excretion of amylase was compared with the excretion of albumin, beta-2 microglobulin and free light chains of immunoglobulins. This investigation showed that amylase is reabsorbed by the tubular cells, but only to a very modest degree compared with the reabsorption of the other three proteins. In the case of amylase only about 45% of the filtered molecules are reabsorbed, whereas more than 90% of the filtered amount of the other molecules is reabsorbed by the tubular cells. The excretion of amylase rose after lysine injection only by a factor 1.8, whereas excretion rose by a factor 28 for albumin, 1,500 for beta-2 microglobulin, 16 for kappa chains and 8 for lambda chains. Minimal values for tubular reabsorption were found to be 5.5 +/- (SD) 4.3 U/min for amylase, 174.0 +/- 35.7 micrograms/min for albumin, 90.5 +/- 14.4 micrograms/min for beta-2-microglobulin, 70.4 +/- 17.4 micrograms/min for kappa chains and 24.2 +/- 9.2 micrograms/min for lambda chains.

Increased urinary excretion of albumin, light chains, and beta2-microglobulin after intravenous arginine administration in normal man

Infusion of 60 g of arginine in six healthy men over a 40-50 min period caused a 16-fold increase in the excretion-rate of albumin from 8-6 to 142-4 mug/min. After injection of 3, 6, 9, and 12 g of arginine the mean albumin-excretion rate of another six normal subjects rose from 5-8 mug/min to 9-4, 13-2, 21-6, and 33-9 mug/min, respectively. Excretion of light chains of immunoglobulin increased from 5-5 mug/min to 18-0, 30-0, 40-5; and 52-0 mug/min, respectively, and the excretion rate of beta2-microglobulin increased from 0-092 mug/min to 2-97, 9-23, 16-39, and 25-71 mug/min. Thus a clear dose response pattern was found. The results strongly suggest that the mechanism behind the arginine-induced protein excretion is an inhibition of tubular reabsorption.

Urinary albumin excretion during exercise in juvenile diabetes. A provocation test for early abnormalities

Urinary albumin excretion during exercise was measured with a radioimmunological method in a group of 13 young male diabetic patients and in a comparable control group. The duration of diabetes was 2-18 years; they had no proteinuria (Albustix¿) and no other signs of renal disease. There was no difference in the basal albumin excretion. In the diabetics the average albumin excretion was doubled during exercise at 600 kpm/min for 20 min, from 9.1 mug/min to 18.7 mug/min (P less than 0.005). No significant change was seen in the controls. These results strongly suggest that abnormal glomerular filter properties are present in patients with relatively short duration of diabetes - that is, in patients who are known to have thickened glomerular basement membrane. The exercise provocation test may be useful in other fields of renal pathophysiology.