Impacts on dialysis therapy

Improvement of clinical outcome of dialysis therapy is a task for everybody working in a dialysis unit. Here we consider dialysis conditions such as choice of treatment parameters and composition of dialysis fluid which may influence clinical outcome of dialysis therapy. Providing 'adequate' dialysis is the aim of the daily work of a dialysis nurse. Haemodialysis parameters with potential impact on dialysis adequacy are discussed with respect to quantification and optimisation. Every year, each patient comes in contact with 20,000 I dialysis fluid during HD treatment. The composition of the fluid, its physical and microbiological quality and their impact on clinical outcome are considered. The function of PD fluid is different from that of an HD fluid thus additional aspects have to be considered regarding its composition. Information is given how the composition and biocompatibility of PD solutions impact the dialysis therapy and how individual patient needs are considered.

Urinary fibronectin excretion in streptozotocin-diabetic rats

Previous investigations performed in human diabetics demonstrate an increase in their urinary fibronectin excretion which was already present in subjects without microalbuminuria and which was elevated prior to functional restrictions. The present study was performed to examine whether in an experimental model these data obtained in men can be confirmed using an animal experimental model, and to further study pathomechanisms of diabetic nephropathy in rats. Fibronectin levels in serum and urine, and renal functional properties such as creatinine clearance, urinary albumin and protein excretion were studied in rats rendered diabetic with streptozotocin and compared with values of control and insulin treated animals for 5 months. Diabetic animals demonstrated the same creatinine clearance, but slightly decreased albumin and total protein excretion rates compared to controls and insulin "treated", euglycaemic animals. Diabetic rats showed a significantly increased excretion following day 42 compared to controls and insulin "treated" group. Concerning serum fibronectin, there was no significant difference between control, diabetic and insulin "treated" animals. The urinary fragment pattern of fibronectin was analyzed qualitatively by immunoblotting pattern and consisted of two main bands (M(r) 66,000 and 45,000). These bands were not altered in controls, insulin "treated" and diabetic rats, independent of the stage of renal involvement in diabetes. Present data provide evidence that fibronectin excretion is elevated in diabetic animals prior to functional restrictions, confirming results obtained in human diabetics. Therefore, determination of urinary fibronectin can serve as a more sensitive indicator for renal involvement in diabetes mellitus than microalbuminuria or changes in glomerular filtration rate. Urinary excretion may therefore serve as an early marker for the renal involvement in diabetes before the onset of clinical symptoms.

Extracellular matrix proteins as early markers in diabetic nephropathy

Basement membrane thickening and mesangial expansion characterize the renal involvement in diabetes mellitus and precede any symptoms of renal dysfunction, e.g., albuminuria and changes in glomerular filtration rate. Since the morphological changes can only be diagnosed by biopsy, this study was designed to investigate whether the urinary excretion of renal extracellular matrix proteins might reflect the morphological alterations. To specify the extent of renal involvement in diabetes, the patients, type I as well as type II diabetics, were classified according to their urinary albumin excretion: normal albumin excretion below 30 micrograms/min, microalbuminuria from 30 to 300 micrograms/min, and overt albuminuria above 200 micrograms/min. Laminin, collagen IV, and fibronectin, all intrinsic components of the renal extracellular matrix, were determined in serum and urine by radioimmunoassay or enzyme-linked-immunosorbent-assay, respectively. The results are given as median values (mean). Additionally, the urinary fragment pattern of fibronectin was analysed qualitatively by immunoblotting. Laminin concentrations in serum and in urine did not change in diabetics. Collagen IV decreased in serum of patients with increased albumin excretion (controls: mean = 255 micrograms/l, normoalbuminuric patients: mean = 56 micrograms/l, microalbuminuric patients: mean = 52 micrograms/l, and patients with overt albuminuria: mean = 70 micrograms/l; alpha < 0.01) and increased in urine (controls, normoalbuminuric and microalbuminuric patients: not detectable, patients with overt albuminuria: mean = 5 ng/12 h; apha < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Origin of urinary fibronectin

BACKGROUND

Fibronectin (FN) is a major component of the glomerular extracellular matrix and it is also abundant in plasma. In physiologic conditions, FN fragments are excreted into urine. Increased urinary FN excretion has been observed in renal diseases raising the question whether urinary FN could reflect changes in the renal extracellular matrix. This study examines whether urinary FN is filtered from plasma or derived from the kidney and it attempts to specify the potential renal source of urinary FN.

EXPERIMENTAL DESIGN

(a) To investigate whether urinary FN is filtered from plasma, labeled, biotinylated FN (b-FN) was injected into rats and urine samples were specifically analyzed for b-FN by an immunoblot procedure. (b) To specify the renal source of urinary FN and to evaluate possible alterations of this protein during passage into final urine, tubular fluid was collected from distinct localizations of the nephron by micropuncture techniques. The samples were analyzed for endogenous FN by a highly sensitive immunoblot system, and the pattern was compared with that normally found in final urine.

RESULTS

(a) Urine samples collected over a period of 5 days after injection of b-FN contained no labeled FN. Control experiments in rats with highly elevated glomerular permeability confirmed that the plasma levels of injected b-FN were sufficiently high since b-FN was detected in urine in this condition. (b) The FN fragment pattern, with two protein bands at 75 and 45 kilodaltons, that is normally found in final urine, was already present in samples taken from the early proximal tubule and the distal tubule.

CONCLUSIONS

The fibronectin fragments normally found in urine originate from the kidney and are not derived from plasma. Since these fragments are already observed in early proximal tubular fluid, the glomerulus is the probable source of urinary FN. The FN fragment pattern of early proximal tubular fluid is not substantially altered during passage into final urine, thus reflecting glomerular FN release in urine. It is suggested that examination of urinary FN excretion could be helpful in the assessment of altered glomerular extracellular matrix in pathologic conditions.

Glycation of serum albumin and its role in renal protein excretion and the development of diabetic nephropathy

The present study was designed to investigate whether microalbuminuria at the onset of diabetic nephropathy might be partially due to the glycation of serum albumin. It is postulated elsewhere (Ghiggeri et al., Proc. Eur. Dial. Transplant. Assoc. 21 (1984) 633-636) that the glycation of serum albumin and the subsequent cationization may induce microalbuminuria. To investigate whether a relationship exists between the amount of glycated albumin in its cationized form and the development, and progression of diabetic nephropathy, the urinary excretion of glycated albumin was studied in diabetic patients. The diabetic patients (type I and II diabetes) were divided into groups according to their albumin excretion rates: group I diabetics had a normal albumin excretion (n = 30, x = 4.2 mg/12 h); group II diabetes displayed microalbuminuria (n = 17, x = 38.6 mg/12 h); group III diabetics displayed macroalbuminuria (n = 21, x = 582.5 mg/12 h). The fraction of glycated albumin in serum (Glyco Gel Test Kit) was 0.032 in group I, 0.042 in group II, and 0.038 in group III, all these values were significantly higher than the value for the controls (0.014%; n = 17, 2 alpha = 0.001) as measured with the Glyco Gel Test Kit. The concentration of glycated albumin in the urine of the controls and group I was below the detection limit. Urine in group II contained only a glycated albumin fraction of 0.0002 of total albumin, and the fraction for group III was 0.0008. Isoelectric focussing (IEF) and chromato-focussing revealed native albumin with an isoelectric point of 4.7-4.9, and anionic glycated albumin with a pI of 3.0-4.2.(ABSTRACT TRUNCATED AT 250 WORDS)