Tubular and glomerular kidney effects in Swedish women with low environmental cadmium exposure

Cadmium is a well-known nephrotoxic agent in food and tobacco, but the exposure level that is critical for kidney effects in the general population is not defined. Within a population-based women's health survey in southern Sweden (Women's Health in the Lund Area, WHILA), we investigated cadmium exposure in relation to tubular and glomerular function, from 1999 through early 2000 in 820 women (71% participation rate) 53-64 years of age. Multiple linear regression showed cadmium in blood (median, 0.38 microg/L) and urine (0.52 microg/L; density adjusted = 0.67 microg/g creatinine) to be significantly associated with effects on renal tubules (as indicated by increased levels of human complex-forming protein and N-acetyl-beta-D-glucosaminidase in urine), after adjusting for age, body mass index, blood lead, diabetes, hypertension, and regular use of nephrotoxic drugs. The associations remained significant even at the low exposure in women who had never smoked. We also found associations with markers of glomerular effects: glomerular filtration rate and creatinine clearance. Significant effects were seen already at a mean urinary cadmium level of 0.6 microg/L (0.8 microg/g creatinine). Cadmium potentiated diabetes-induced effects on kidney. In conclusion, tubular renal effects occurred at lower cadmium levels than previously demonstrated, and more important, glomerular effects were also observed. Although the effects were small, they may represent early signs of adverse effects, affecting large segments of the population. Subjects with diabetes seem to be at increased risk.

Pheromone binding to two rodent urinary proteins revealed by X-ray crystallography

The principal protein excreted in male rat urine, urinary alpha 2-globulin and the homologous mouse protein, major urinary protein, have been well characterized, although their functions remain unclear. Male rat urine affects the behaviour and sexual response of female rats, leading to the proposal that rodent urinary proteins are responsible for binding pheromones and their subsequent release from drying urine. Urinary alpha 2-globulin is also involved in hyaline droplet nephropathy, an important toxicological syndrome in male rats resulting from exposure to a number of industrial chemicals and characterized by the accumulation of liganded urinary alpha 2-globulin in lysosomes in the kidney, followed by the induction of renal cancer. We now report the three-dimensional structures of mouse major urinary protein (at 2.4 A resolution) and rat urinary alpha 2-globulin (at 2.8 A resolution). The results corroborate the role of these proteins in pheromone transport and elaborate the structural basis of ligand binding.

Low level exposure to cadmium and early kidney damage: the OSCAR study

OBJECTIVES

To study the dose-response relation between cadmium dose and renal tubular damage in a population of workers and people environmentally or occupationally exposed to low concentrations of cadmium.

METHODS

Early kidney damage in 1021 people, occupationally or environmentally exposed to cadmium, was assessed from cadmium in urine to estimate dose, and protein HC (alpha(1)-microglobulin) in urine to assess tubular proteinuria.

RESULTS

There was an age and sex adjusted correlation between cadmium in urine and urinary protein HC. The prevalence of tubular proteinuria ranged from 5% among unexposed people to 50% in the most exposed group. The corresponding prevalence odds ratio was 6.0 (95% confidence interval (95% CI) 1.6 to 22) for the highest exposure group, adjusted for age and sex. Multiple logistic regression analysis showed an increasing prevalence of tubular proteinuria with urinary cadmium as well as with age. After adjustment to the mean age of the study population (53 years), the results show an increased prevalence of 10% tubular proteinuria (taking into account a background prevalence of 5%) at a urinary cadmium concentration of 1.0 nmol/mmol creatinine.

CONCLUSION

Renal tubular damage due to exposure to cadmium develops at lower levels of cadmium body burden than previously anticipated.

Low-level cadmium exposure and osteoporosis

Osteoporosis is a major cause of morbidity worldwide. A number of risk factors, such as age and gender, are well established. High cadmium exposure causes renal damage and in severe cases also causes osteoporosis and osteomalacia. We have examined whether long-term low-level cadmium exposure increases the risk of osteoporosis. Bone mineral density (BMD) in the forearm was measured in 520 men and 544 women, aged 16-81 years, environmentally or occupationally exposed to cadmium, using dual-energy X-ray absorptiometry (DXA) technique. Cadmium in urine was used as the dose estimate and protein HC was used as a marker of renal tubular damage. There was a clear dose-response relation between cadmium dose and the prevalence of tubular proteinuria. Inverse relations were found between cadmium dose, tubular proteinuria, and BMD, particularly apparent in persons over 60 years of age. There was a dose-response relation between cadmium dose and osteoporosis. The odds ratios (ORs) for men were 2.2 (95% CI, 1.0-4.8) in the dose group 0.5-3 nmol Cd/mmol creatinine and 5.3 (2.0-14) in the highest dose category (> or = 3 nmol/mmol creatinine) compared with the lowest dose group (< 0.5 nmol Cd/mmol creatinine). For women, the OR was 1.8 (0.65-5.3) in the dose group 0.5-3 nmol Cd/mmol creatinine. We conclude that exposure to low levels of cadmium is associated with an increased risk of osteoporosis.

The effect of reduced glomerular filtration rate on plasma total homocysteine concentration

The concentration of homocysteine in plasma has been shown to be increased in renal failure, possibly contributing to the accelerated atherosclerosis observed in uraemic patients. The aim of the present study was to document the relationship between plasma total homocysteine (tHcy) concentrations and glomerular filtration rates (GFR) in highly selected patients, with renal function ranging from normal to dialysis dependency. GFR was defined as the plasma clearance of iohexol; a more accurate method than the creatinine-based estimations applied in previous studies. Plasma tHcy concentrations were highly correlated to GFR (r = -0.70, p < 0.0001) and were significantly increased already in moderate renal failure. According to a multiple regression analysis, GFR and red cell folate concentrations independently predicted plasma tHcy concentrations, whereas those of serum creatinine, plasma pyridoxal-5-phosphate, urine albumin and urine alpha-1-microglobulin (a marker of tubular damage) did not. Thus, GFR seems to be a better determinant of plasma tHcy concentration than serum creatinine concentration. Plasma total cysteine and total cysteinylglycine concentrations followed the same pattern as those of tHcy.

Major urinary proteins, alpha(2U)-globulins and aphrodisin

The major urinary proteins (MUPs) are proteins secreted by the liver and filtered by the kidneys into the urine of adult male mice and rats, the MUPs of rats being also referred to as alpha(2U)-globulins. The MUP family also comprises closely related proteins excreted by exocrine glands of rodents, independently of their sex. The MUP family is an expression of a multi-gene family. There is complex hormonal and tissue-specific regulation of MUP gene expression. The multi-gene family and its outflow are characterized by a polymorphism which extends over species, strains, sexes, and individuals. There is evidence of evolutionary conservation of the genes and their outflow within the species and evidence of change between species. MUPs share the eight-stranded beta-barrel structure lining a hydrophobic pocket, common to lipocalins. There is also a high degree of structural conservation between mouse and rat MUPs. MUPs bind small natural odorant molecules in the hydrophobic pocket with medium affinity in the 10(4)-10(5) M(-1) range, and are excreted in the field, with bound odorants. The odorants are then released slowly in air giving a long lasting olfactory trace to the spot. MUPs seem to play complex roles in chemosensory signalling among rodents, functioning as odorant carriers as well as proteins that prime endocrine reactions in female conspecifics. Aphrodisin is a lipocalin, found in hamster vaginal discharge, which stimulates male copulatory behaviour. Aphrodisin does not seem to bind odorants and no polymorphism has been shown. Both MUPs and aphrodisin stimulate the vomeronasal organ of conspecifics.

Alpha-1-microglobulin: an indicator protein for renal tubular function

A comparison of urinary alpha 1-microglobulin concentrations to the behaviour of other indicators of renal tubular disorders, beta 2-microglobulin, retinol-binding protein and N-acetyl-beta-D-glucosaminidase (NAG) has been made. In acute tubular disorders the concentrations of urinary beta 2M and RBP are highly correlated (r = 0.89) but this is less marked for alpha 1M and beta 2M (r = 0.55) and alpha 1M and RBP r = 0.48. NAG tends to run a parallel course to alpha 1M concentrations but lags behind the recovery of low molecular weight protein reabsorption following injury of the tubular cells. The concentrations of alpha 1M, and in particular its stability at low pH suggest that this protein may be useful in screening for tubular abnormalities and detecting chronic asymptomatic renal tubular dysfunction. Urinary alpha 1M greater than 15 mg/g creatinine is strongly suspicious of a proximal tubular dysfunction. The distinction between pure tubular proteinuria and mixed glomerular and tubular proteinuria requires further analysis.

Selective activation of G protein subtypes in the vomeronasal organ upon stimulation with urine-derived compounds

Chemosensory neurons in the vomeronasal organ (VNO) detect pheromones related to social and reproductive behavior in most terrestrial vertebrates. Current evidence indicate that the chemoelectrical transduction process is mediated by G protein-coupled second messenger cascades. In the present study, attempts were made to identify the G protein subtypes which are activated upon stimulation with urinary pheromonal components. G protein-specific antibodies were employed to interfere specifically with inositol 1,3,4-trisphosphate formation induced by urinary stimuli and to immunoprecipitate Galpha-subunits, activation dependently labeled with [alpha-32P]GTP azidoanilide. The results of both experimental approaches indicate that stimulation of female VNO membrane preparations with male urine samples induces activation of Gi as well as Go subtypes. Experiments using different fractions of urine revealed that upon stimulation with lipophilic volatile odorants, only Gi proteins were activated, whereas Go activation was elicited by alpha2u-globulin, a major urinary protein, which is a member of the lipocalin superfamily. Since each G protein subtype is stereotypically coexpressed with one of the two structurally different candidate pheromone receptors (V1R and V2R), the results provide the first experimental evidence that V1Rs coexpressed with Gi may be activated by lipophilic probably volatile odorants, whereas V2Rs coexpressed with Go seem to be specialized to interact with pheromonal components of proteinaceous nature.

Hormonal regulation of the hepatic messenger RNA levels for alpha2u globulin

The messenger RNA rat alpha2u globulin has been identified and quantitated in a cell-free translational system derived from Krebs II ascites cells. Hepatic tissue of the mature male rats which normally produce alpha2u globulin was also found to contain a high level of alpha2u mRNA. Approximately 1.6 per cent of all poly(A) containing RNA of the adult male rat liver could be accounted for alpha2u messenger activity. Female rats do not produce alpha2u globulin and no alpha2u mRNA activity could be detected in the poly(A) containing RNA fraction obtained from the livers of these animals. However, androgen treatment to spayed female rats was found to induce the parallel appearance to both alpha2u globulin and its corresponding mRNA. Both hypophysectomy and adrenalectomy which are known to reduce the level of alpha2u globulin in the urine of male rats were found also to reduce the hepatic level of alpha2u mRNA. The results indicate that hormonal control of alpha2u globulin synthesis in rat liver is achieved primarily through regulation of its translatable mRNA level and that more than one hormone may participate in this regulation.

Markers of diabetic nephropathy

It is well established that the detection of microalbuminuria in a patient with diabetes mellitus indicates the presence of glomerular involvement in early renal damage. Recent studies have demonstrated that there is also a tubular component to renal complications of diabetes, as shown by the detection of renal tubular proteins and enzymes in the urine. In fact, tubular involvement may precede glomerular involvement, as several of these tubular proteins and enzymes are detectable even before the appearance of microalbuminuria. This review looks at the studies reported so far on serum and urinary markers of diabetic nephropathy, both glomerular and tubular, and their roles in the early detection of renal damage. The advantages and disadvantages of some of these markers are also discussed. The markers reviewed include (1) glomerular--transferrin, fibronectin, and other components of glomerular extracellular matrix, and (2) tubular--low molecular weight proteins (beta 2 microglobulin, retinol binding protein, alpha 1 microglobulin, urine protein 1), other proteins such as Tamm-Horsfall protein, beta 2 glycoprotein-1, urinary enzymes (N-acetyl-beta-D-glucosaminidase, cholinesterase, gamma glutamyltranspeptidase, alanine aminopeptidase), and tubular brush-border antigen.

Low level cadmium exposure, renal and bone effects--the OSCAR study

It is well known that high cadmium exposure causes renal damage, osteoporosis and osteomalacia, whereas the dose-response relationships at low-level exposure are less well established. WHO estimated (1992) that a urinary excretion of 10 nmol/mmol creatinine would constitute a 'critical limit' below which kidney damage would not occur. Later, Belgian and Swedish studies have shown signs of cadmium induced kidney dysfunction in the general population already at urinary cadmium levels around 2-3 nmol/mmol creatinine. The Swedish OSCAR (OSteoporosis-CAdmium as a Risk factor) study comprised 1021 individuals, exposed to cadmium in the environment. Blood and urinary cadmium were used as dose estimates. Protein HC (alpha-1-microglobulin) was used as an indicator of renal tubular damage. Forearm bone mineral density (BMD) was assessed with DXA (dual energy x-ray absorptiometry) technique. The study showed that tubular proteinuria occurred at much lower levels of cadmium dose than previously known. A negative dose-effect relationship was found between cadmium dose and BMD for people at the age of 60 or older. In this age group, there was also a dose-response relationship, showing a three-fold increased risk of low BMD in the group with urinary cadmium over 3 nmol/mol creatinine, as compared to the lowest dose group. There was also evidence of an increased risk of forearm fractures with increasing cadmium levels in the population 50 years of age or older. The potential public health consequences of low level cadmium exposure should be recognized, and measures taken to reduce cadmium exposure to an absolute minimum.

Alpha 1-microglobulin: clinical laboratory aspects and applications

BACKGROUND

Urinary microproteins are becoming increasingly important in clinical diagnostics. They can contribute in the non-invasive early detection of renal abnormalities and the differentiation of various nephrological and urological pathologies. Alpha 1-microglobulin (A1M) is an immunomodulatory protein with a broad spectrum of possible clinical applications and seems a promising marker for evaluation of tubular function.

METHOD

We performed a systematic review of the peer-reviewed literature (until end of November 2003) on A1M with emphasis on clinical diagnostic utility and laboratory aspects.

CONCLUSIONS

A1M is a 27-kDa glycoprotein, present in various body fluids, with unknown exact biological function. The protein acts as a mediator of bacterial adhesion to polymer surfaces and is involved in inhibiting renal lithogenesis. Because A1M is not an acute phase protein, is stable in a broad range of physiological conditions and sensitive immunoassays have been developed, its measurement can be used for clinical purposes. Unfortunately, international standardisation is still lacking. Altered plasma/serum levels are usually due to impaired liver or kidney functions but are also observed in clinical conditions such as HIV and mood disorders. Urinary A1M provides a non-invasive, inexpensive diagnostic alternative for the diagnosis and monitoring of urinary tract disorders (early detection of tubular disorders such as heavy metal intoxications, diabetic nephropathy, urinary outflow disorders and pyelonephritis).

Respiratory allergy to urine proteins of rats and mice

Five atopic laboratory workers with asthma and other manifestations of allergy to rats and mice were sensitive to low-molecular-weight urine proteins--an alpha2-globulin in the rat and a prealbumin in the mouse. Positive skin prick and inhalation test reactions to the urine proteins were obtained; and radioallergosorbent tests (R.A.S.T.) for specific IgE antibody were also positive. These findings show that proper control of the collection and disposal of the animals' urine is necessary to minimise the likelihood of sensitisation.

Idiopathic Membranous Nephropathy: Outline and Rationale of a Treatment Strategy

Idiopathic membranous nephropathy is a common cause of nephrotic syndrome. The treatment of patients with idiopathic membranous nephropathy is heavily debated. Based on literature data and our own experience, we propose a rational treatment strategy. Patients with renal insufficiency (serum creatinine level > 1.5 mg/dL [> 135 micromol/L]) are at greatest risk for the development of end-stage renal disease and should receive immunosuppressive therapy. In patients with normal renal function (serum creatinine level < 1.5 mg/dL [< 135 micromol/L]), risk for developing end-stage renal disease can be estimated by measuring urinary excretion of beta2-microglobulin or alpha1-microglobulin and immunoglobulin G. For low-risk patients, a wait-and-see policy is advised. High-risk patients likely benefit from immunosuppressive therapy. Currently, combinations of steroids with chlorambucil or cyclophosphamide are the best studied. We prefer cyclophosphamide in view of its fewer side effects. Cyclosporine may be an alternative option in patients with well-preserved renal function, although long-term data are lacking. Other immunosuppressive agents, such as mycophenolate mofetil or rituximab, currently are under study; however, data are insufficient to support their routine use.

Urinary alpha1-microglobulin as a marker of nephropathy in type 2 diabetic Asian subjects in Singapore

OBJECTIVE

This study examines urinary alpha(1)-microglobulin as a marker of early nephropathy in type 2 diabetic Chinese, Malays, and Asian Indians in Singapore.

RESEARCH DESIGN AND METHODS

A cross-sectional study was performed on 590 consecutive type 2 diabetic patients (296 males, 294 females) who were on routine follow-up at a primary care clinic. Information was obtained from interviews, case notes, and blood and urine samples. Because the distribution of urinary alpha(1)-microglobulin levels was highly skewed, these levels were log-transformed, and geometric means were calculated. There was correction for variability in urine flow by dividing by urine creatinine levels, given as mg/mmol urine creatinine, and adjustment for confounding variables.

RESULTS

Urinary alpha(1)-microglobulin was higher in men than in women and was directly related to age, but no ethnic differences were apparent. It was directly related to duration of diabetes, with adjusted geometric means of 1.19 and 1.43 mg/mmol urine creatinine for a duration of <10 and > or =10 years, respectively (P = 0.07). Urinary alpha(1)-microglobulin was highest in patients on insulin, followed by those on oral medication and then those on diet alone (adjusted geometric means: 1.47, 1.36, and 0.86 mg/mmol urine creatinine, respectively; P = 0.01). Levels were also higher in patients with poor glucose control, as measured by HbA(1c), fasting plasma glucose, and 2-h postprandial plasma glucose (P < 0.01 for each). Urinary alpha(1)-microglobulin was directly related to albuminuria, with adjusted geometric means for normoalbuminuria, microalbuminuria, and macroalbuminuria of 1.06, 1.47, and 4.72 mg/mmol urine creatinine, respectively (P < 0.01). However, of patients with normoalbuminuria, 33.6% had raised urinary alpha(1)-microglobulin. Likewise, of patients with normal urinary alpha(1)-microglobulin, 27.6% had albuminuria.

CONCLUSIONS

Urinary alpha(1)-microglobulin was related to duration, severity, and control of diabetes. Urinary alpha(1)-microglobulin and albumin were directly related, but in some patients, one was present in the absence of the other. Hence, in addition to albuminuria (which measures glomerular dysfunction), urinary alpha(1)-microglobulin (which measures proximal tubular dysfunction) is useful for the early detection of nephropathy in diabetic subjects.

Effects of a dimeric vs a monomeric nonionic contrast medium on renal function in patients with mild to moderate renal insufficiency: a double-blind, randomized clinical trial

The efficacy and safety of nonionic dimeric contrast media in subjects with impaired renal function is largely unknown. The present study was aimed at determining the risk of tubular nephrotoxicity in patients with mild to moderate renal insufficiency who underwent intravenous urography (IVU) with the nonionic dimeric contrast agent iodixanol (Visipaque, Nycomed Imaging, Oslo, Norway). In a double-blind protocol 64 patients (55 males; mean age 68.3 years) with serum creatinine between 135 and 265 micromol/l who were to undergo IVU were randomized to receive iodixanol (a nonionic dimer) or iopromide (a nonionic monomer), 600 mg I/kg b. w. Renal function was evaluated before and 1 h, 6 h, 24 h, 48 h and 7 days after IVU with analysis of serum creatinine, urinary enzymes alanylaminopeptidase and N-acetyl-beta-glucosaminidase, and urinary microproteins alpha-1-microglobulin and albumin. Renal function remained stable in both contrast medium groups during the follow-up period. No statistically significant differences were observed between the monomer and the dimer in terms of urinary enzyme and microprotein excretion or serum creatinine. Transient radiocontrast-induced nephropathy developed in 1 patient who had received iodixanol. The administration of the nonionic dimeric contrast medium iodixanol, or of the nonionic monomer iopromide, entailed a low nephrotoxic potential in patients with mild to moderate renal insufficiency undergoing excretory urography.

Urinary excretion of IgG and alpha(1)-microglobulin predicts clinical course better than extent of proteinuria in membranous nephropathy

In idiopathic membranous nephropathy (MN), the main predictors for progression to chronic renal failure (CRF) are the amount of proteinuria and extent of tubulointerstitial damage. The aim of this study is to evaluate whether urinary excretion of proteins reflecting the alteration of permselectivity in the glomerular capillary wall, such as immunoglobulin G (IgG), and the reabsorption impairment of low-molecular-weight proteins, such as alpha(1)-microglobulin (alpha(1)m), correlates with the extent of tubulointerstitial damage and have a predictive value for functional outcome and response to therapy better than 24-hour proteinuria. In 78 patients with MN, urinary excretion of albumin, transferrin, IgG, and alpha(1)m was measured by immunonephelometry in second-morning urine samples and expressed in milligrams per gram of urinary creatinine (uCr). In 48 patients with characterization of proteinuria and renal biopsy performed at the same time, excretion of IgG (P = 0.0087) and alpha(1)m (P = 0.0024), but not albumin (P = 0.37), transferrin (P = 0.38), or 24-hour proteinuria (P = 0.32), was associated significantly with the extent of tubulointerstitial damage (score, 0 to 1 versus >/=2). Only alpha(1)m excretion was associated significantly with global glomerular sclerosis (P = 0.0032) and arteriolar hyalinosis (P = 0.0004). Moreover, urinary excretion of alpha(1)m was significantly dependent on IgG excretion (r = 0.67; P = 0.0001), but not on albumin (P = 0.66) or 24-hour proteinuria (P = 0.07). Functional outcome could be evaluated in 38 patients with nephrotic syndrome and baseline normal renal function (serum creatinine, 0.99 +/- 0.20 mg/dL; follow-up, 44 +/- 22 months). Remission was 100% versus 20% in patients with IgG excretion less than 110 mg/g uCr versus 110 mg/g uCr or greater (P = 0.0001) and 77% versus 17% in patients with alpha(1)m excretion less than 33.5 mg/g uCr versus 33.5 mg/g uCr or greater (P = 0.0009), respectively. In patients with IgG and alpha(1)m excretion less than or greater than the cutoff value, progression to CRF was 0% versus 35% (P = 0.0026) and 0% versus 58% (P = 0.0001), respectively. Nineteen patients treated with immunosuppressive therapy were compared with 19 untreated patients. There was no difference in remission or progression between treated and untreated patients when IgG and alpha(1)m excretion were less than the cutoff value. There was a significant difference for progression to CRF between treated and untreated patients when alpha(1)m excretion was greater than the cutoff value (17% versus 100%; P = 0.0076). In conclusion, IgG excretion is associated significantly with the extent of tubulointerstitial damage and alpha(1)m excretion. This observation supports the hypothesis that IgG may be the toxic moiety of proteinuria. Excretion of IgG and alpha(1)m has a significant predictive value for both remission and progression and is useful to identify patients who are at risk for progression and for whom treatment with immunosuppressive therapy is indicated soon after diagnosis.

Low-level cadmium exposure and effects on kidney function

OBJECTIVES

The nephrotoxicity of cadmium at low levels of exposure, measured by urinary cadmium, has recently been questioned since co-excretion of cadmium and proteins may have causes other than cadmium toxicity. The aim of this study was to explore the relation between kidney function and low or moderate cadmium levels, measured directly in kidney biopsies.

METHODS

We analysed cadmium in kidney biopsies (K-Cd), blood (B-Cd) and urine (U-Cd) from 109 living kidney donors in a cross-sectional study. We measured glomerular filtration rate (GFR), cystatin C in serum, albumin, β-2-microglobulin (B2M), retinol-binding protein (RBP), α-1-microglobulin (A1M), N-acetyl-β-d-glucosaminidase and kidney injury molecule 1 (KIM-1) in 24 h and overnight urine.

RESULTS

We found significant positive associations between A1M excretion and K-Cd in multiple regression models including age, sex, weight, smoking and urinary flow rate. This association was also present in never-smokers. A1M was also positively associated with B-Cd and U-Cd. GFR and the other biomarkers of kidney function were not associated with K-Cd. GFR estimated from serum cystatin C showed a very poor correlation with measured GFR. KIM-1, RBP and possibly albumin were positively associated with U-Cd, but only in overnight urine. No associations were found with B2M.

CONCLUSIONS

Our results suggest that A1M in urine is a sensitive biomarker for effects of low-level cadmium exposure. A few associations between other renal biomarkers and U-Cd, but not K-Cd, were probably caused by physiological co-excretion or chance.

Androgen-dependent synthesis of aplha-2u globulin in the rat: role of the pituitary gland

Hypophysectomy completely abolished the androgen-dependent synthesis of α2u globulin in adult rats. Experiments with adrenalectomized and thyroidectomized adult male rats showed that these endocrine ablations also reduced the daily urinary output of α2u globulin to about 10% or less than those of the pre-operative values. The effects of adrenalectomy and thyroidectomy on α2u output could be reversed to normal with the supplementation of corticosterone and thyroxine respectively. However, none of the pituitary hormones administered alone or along with testosterone was able to reverse the effect of hypophysectomy. Simultaneous treatment with growth hormone, corticosterone and thyroxine along with testosterone was required for the complete reversal of the effect of hypophysectomy. It is concluded that the androgenic induction of α2u globulin is dependent on the synergistic effects of growth and developmental hormones such as growth hormone, thyroxine and corticosterone.

Stability of alpha 1-microglobulin, beta 2-microglobulin and retinol binding protein in urine

The stability of alpha 1-microglobulin (alpha 1M), beta 2-microglobulin (beta 2M) and retinol binding protein (RBP) in urine was determined in 135 random samples from children with renal disease, febrile illness, malignancy, and from controls. Immediately after voiding, samples were divided into two portions, one of which was alkalinized. After identical transit times and laboratory handling the pH and concentrations of the individual proteins in each pair were measured. beta 2M was unstable in urine of pH less than 7 and grossly so below pH 6. In some instances beta 2M was low or undetectable even in the alkalinized samples when alpha 1M and RBP levels were raised, suggesting that degradation of beta 2M may have occurred prior to voiding. Concentrations of alpha 1M and RBP were significantly lower in the non-alkalinized fractions at pH less than 7, although to lesser degree than for beta 2M. Contrary to previous reports, we conclude that the stability of all 3 proteins is affected by urinary pH and recommend that this be measured and alkalinisation performed at the time of voiding.

Alpha 2u-globulin nephropathy: review of the cellular and molecular mechanisms involved and their implications for human risk assessment

This paper reviews what is known about the induction of alpha 2u-globulin nephropathy and carcinogenesis. This unique male-rat-specific disease is associated with exposure to an ever-increasing number of chemicals. The processes leading to nephropathy and renal cancer are among the best-understood mechanisms for nongenotoxic chemicals and strongly support that it is a male-rat-specific process that is not relevant for human risk assessment. Nevertheless, the data available for individual chemicals vary greatly. This necessitates a case-by-case analysis of the available data when determining the relevance for humans of this chemically induced renal disease in male rats.