Current problems in clinical biochemistry最新文献

Cephalosporins have a distinctly different effect from that of aminoglycosides on membranes of the proximal tubule of the human kidney as measured by urinary AAP concentrations. Except for a slight influence by cephacetrile, cephalosporins showed no effect on the proximal tubule. In contrast, after three days of administration, the aminoglycosides caused a cumulative increase in membrane proteins of the proximal tubule to be excreted in the urine. Tobramycin appears to have the least and amikacin the greatest effect on the brush border membranes of the proximal tubule of the normal human kidney. The combination of cephalosporins with aminoglycosides increases the potential toxic effect on the proximal tubule.

From previous investigations with nephroptotic patients increased urinary LDH was assumed to be a reliable marker indicating a renal tissue defect due to the organs descent in erect position. Animal experiments now allowed correlation of this enzymatic activity with controlled changes of anatomical and physiological parameters. Changes of the renal hemodynamics or urinary flow induced in acute experiments in dogs simulated kidney displacement in nephroptotic patients. Both ureters were cannulated for separate urine collection and one kidney was manipulated. The renal arterial or venous flow was reduced or the ureter was occluded under electromagnetic blood-flow control. Arterial constriction alone (30%/15 min) selectively caused a drastic decrease (approximately 80%) of Xenon wash-out (= nutrient-flow) in the renal cortex. Under the same conditions radio-labeled microspheres injected intracardially showed a centralization of the renal capillary blood flow from the outer cortex to the juxtamedullary zone. Urinary LDH activities increased up to 800% immediately after arterial constriction. In accordance with total LDH activity the percentage distribution of isoenzymes changed: LDH-I increased and the LDH-V decreased. Neither constriction of the renal vein nor ureteral occlusion had similar effects. In long-term experiments backward fixation of one kidney in rats would reflect the effects of kidney displacement over years in nephroptotic patients: animals were unilaterally nephrectomized and the remaining kidney was dislocated backwards (approximately 2,5 vertebrae) and fixed to the lateral pelvic wall. "Ptotic" rats showed during the following examinations a constant increase of urinary LDH up to 50% by 26 weeks postoperatively. In accordance with increased LDH the isotope nephrogram was pathological and arteriographies showed a stretched and narrowed renal artery. In a number of rats "ptotic" fixation was not effective enough. All these animals showed normal LDH, isotope nephrograms and arteriographies. Both animal experiments documented that reduced flow/hypoxia is essentially responsible for the tissue damage in the kidney manifested by increased release of urinary LDH.

Three electrophoretic techniques are usually available in the clinical laboratories for the qualitative investigation of urinary protein patterns: 1) acetate cellulose, 2) immuno-electrophoresis; and 3) SDS-polyacrylamide gel electrophoresis. Proteinuria (the excretion of proteins in excess of 150 mg/day or 100 microgram/min) usually signifies either increased permeability of the glomerular-capillary membrane of diminished tubular reabsorption. Since glomerular disease is associated with an increased clearance of albumin and higher molecular weight proteins, whereas tubular damage is associated with the predominant excretion of proteins of lower molecular weight than albumin, it seems logical to establish a classification of proteinuria according to the molecular weight of its constituents. One can thus basically distinguish 5 types of proteinurias: 1) physiological; 2) tubular; 3) selective glomerular; 4) non selective glomerular; and 5) mixed proteinurias. Additionally one must distinguish "myeloma proteinurias" where monoclonal complete or incomplete gamma-globulins are found in the urine. Clinically it may be useful to determine the qualitatively normal or pathologic character of a quantitatively normal proteinuria, especially in the following conditions: 1) for early diagnosis of nephropathy in patients, such as diabetics, which are particularly prone to suffer from renal complications; 2) to confirm the clinical cure or to predict the recurrence of renal diseases; and 3) in such situations as orthostatic, or myeloma proteinuria, or any elevation of the urinary protein output of unknown etiology.

Male rats were housed singly in metabolic cages, injected i.v. with cephaloridine, 24 h urine samples collected successively; then the rats were killed for obtaining the kidneys of corresponding animals. The concentrations of protein, aminopeptidase (AP), alkaline phosphatase (aPP), lactic dehydrogenase (LDH), and aldolase (ALD) were determined in urine and the percentages of injured proximal tubules counted in sections stained for aPP. The results from individual animals were: (1) After placing animals singly in metabolic cages large but not systematic changes of urinary enzyme concentrations occurred. After 6-10 days the enzymes reached steady state levels. (2) After a single injection of cephaloridine a dose dependent injury of proximal tubules was observed, the urinary LDH content correlating best with the tubular injury (r greater than 0.93) and giving up to 1,000 fold increases above normal values. (3) A circadian rhythm of the susceptibility of rat kidney for cephaloridine was observed, the smallest response was seen when the animals were injected at 7 a.m. and the largest after injection at 7 p.m. (4) In subacute toxicity studies urinary LDH was increased on day 2 above the extent after a single dose, but declined on day 3 to reach normal levels after 8 to 10 days (time of sacrifice). The kidneys revealed practically normal histology. The other enzymes studied had also returned to normal values. This indicates some adaptation mechanism.

The urinary excretion of lactate dehydrogenase, gamma-glutamyltransferase, alkaline phosphatase, arylsulphatase A, alpha-glucosidase, beta-galactosidase, trehalase, N-acetyl-beta-glucosaminidase, beta-glucuronidase, and leucine arylamidase was studied in 68 patients with biopsy-proved glomerular, 54 with interstitial renal disease and in 97 patients suffering from primary hypertension. The enzyme output of these 219 patients was compared to that of a reference population of 100 thoroughly selected healthy subjects. The highest incidence of elevated enzyme excretion was observed for N-acetyl-beta-glucosaminidase with 88% in glomerulopathies and 78% in interstitial disease, followed by beta-galactosidase. 94% of the patients with glomerular kidney disease, 90% of those with interstitial disease and about 60% of the subjects with primary benign hypertension revealed an output of at least one enzyme above upper reference limit. The highest average enzymuria occured in glomerulopathies, particularly high values in patients with the nephrotic syndrome. Application of discriminant analysis to the urinary enzyme pattern of glomerular and interstitial renal diseases resulted in an overall correct classification into the appropriate group of 89% of all patients. The discrimination between glomerular and interstitial disease was better in patients with normal renal function than in those with reduced function. Results show, that the analysis of urinary enzyme patterns may be a helpful adjunct for differential diagnosis of kidney diseases.

An essential part of the classification of prostate carcinoma is the diagnosis of bone metastases. This was done with 70 patients using x-ray analysis, scintography, determination of the acid and alkaline phosphatase, and pelvic crest biopsy, as well as aspiration of the pelvic and sternal bone marrow. In addition, the hydroxyproline concentration was determined in the 24-hour-urine. The study, which was initially undertaken on a sample group (n = 145), yielded a high correlation between age and sex and hydroxyproline values. Women before menopause show significantly lower values than do men of the same age. The data on patients with prostata cancer (n = 70) showed that patients with and without bone metastases, who had been treated with estrogens, had a significantly lower quantity of hydroxyproline than did patients who had not received estrogen therapy. Patients with skeletal metastases (n = 24) showed significantly higher hydroxyproline excretion in the urine than did those with prostate cancer without metastases, or healthy men of the same age (n = 35). Comparison of the results of hydroxyproline determination with the other diagnostic methods for demonstrating bone metastases showed that hydroxyproline determination was diagnostically on par with the scintigram. Pelvic crest biopsy, pelvic and sternal marrow aspiration can be considered valuable supplementary diagnostic procedures.

Three types of low molecular weight serum proteins, myoglobin, hemoglobin and BENCE-JONES proteins, are associated clinically with acute renal failure. All have isoelectric points which render them anionic at blood pH but cationic in the distal nephron under conditions of aciduria. Experiments in which these proteins were mixed with TAMM-HORSFALL mucoprotein in vitro and the pH lowered with lN HCl showed co-precipitation of proteins at pH levels of 5.5 and below. In vivo experiments in which 11 different BENCE-JONES proteins of pl ranging from 5.2 to 6.6 were injected into aciduric, hydropenic rats showed an acute rise in serum urea nitrogen and creatinine concentrations with BENCE-JONES proteins of pl greater than 5.7 compared with little change in rats injected with BENCE-JONES proteins of pl less than 5.7. These data suggest that protein pl and urine pH are important in determining nephrotoxicity; a mechanism by which these low molecular weight serum proteins and TAMM-HORSFALL proteins interact in the distal nephron to initiate acute renal failure in postulated.

The relative merits of the automated, fluorimetric assay of urinary enzymes and cell exfoliation were compared with other commonly used tests for renal damage. Two types of nephrotoxic agent were used, causing crystal nephropathy and acute tubular necrosis respectively. Groups of marmosets were given one of two drugs known to cause crystal nephropathy. One agent caused intermittent increases in urinary enzyme excretion and an early increase in cell excretion which was not sustained. The second agent in contrast caused elevated cell and enzyme excretion, increasing throughout the period of administration. A nephrotoxic anti-tumour agent also caused increases in cell and enzyme excretion when given to marmosets. The early changes produced by this agent were studied using catheterised rats. Hourly samples of urine were collected and urinary beta-glycosidase excretion was found to give an early indication of renal damage, which correlated with albuminuria and glycosuria. The fluorimetric assay of urinary enzymes provides a sensitive, non-invasive test of nephrotoxicity.

The isolated rectal gland of the spiny dogfish is a unique model for the study of active chloride transport. The gland is stimulated to secrete chloride agains an electrical and a chemical gradient when perfused in vitro by theophylline and/or dibutyryl cyclic AMP. Chloride secretion is depressed by ouabain which inhibits Na-K-ATPase. Thiocyanate and furosemide also inhibit chloride secretion but ethoxolamide, a carbonic anhydrase inhibitor, does not. Chloride transport is highly dependent on sodium concentration in the perfusate. The intracellular concentration of chloride in intact glands exceeds the level expected at electrochemical equilibrium, suggesting active transport of chloride into the cell. These features suggest a general hypothesis for chloride secretion in which the uphill transport of chloride into the cytoplasm is coupled through a membrane carrier to the downhill movement of sodium along its electrochemical gradient. The latter is maintained by the Na-K-ATPase pump while chloride is extruded into the duct by electrical forces.

An antibody was raised in rabbits against NaI extracted plasma membranes of rat kidney. The antibody inhibited (Na+K+)-ATPase of basolateral membranes and of rat erythrocyte ghosts. Also K+-stimulated pNPase was inhibited. No effect on Mg-ATPase and basal pNPase activity was registered. Kinetic experiments with Na+,K+ and Mg-ATP showed a noncompetitive inhibition of (Na+K+)-ATPase by the antibody. Hill constants were unchanged. In renal epithelial cell cultures as well as in intact rat erythrocytes ouabain sensitive 22Na-efflux and 42K influx was inhibited by the antibody. It is concluded that outward facing Na+K+-ATPase is immunogenic. The antibody can be raised when the antigen is adequately disintegrated to open otherwise hidden antigenic sites.