The urinary excretion of enzymes following repeated parenteral administration of cadmium to rats

Time course of chronic oral cadmium nephrotoxicity in Wistar rats: excretion of urinary enzymes

Twelve male and female Wistar rats each received cadmium (as CdCl2) in their diet at concentrations of 0, 10, 50, and 250 ppm for 72 weeks. After 1, 4, 8, 13, 18, 26, 32, 45, 57, and 68 weeks a total of 8 enzymes from different cellular compartments of the nephron were measured. At the end of the study period, the kidneys were examined histopathologically. Concentrations up to and including 50 ppm did not induce any adverse effect. At 250 ppm, growth of male and female animals was markedly retarded. Significantly increased activities of the cytosolic phosphohexose isomerase were excreted by males and females receiving 250 ppm at all timepoints from week 13. The values of the mitochondrial glutamate dehydrogenase were mostly elevated from week 1 to 57, however, due to a wide scatter range, were only occasionally significantly different from control values. The brush border enzymes (gamma-glutamyl transferase, alkaline phosphatase and leucine arylamidase) were not changed in a relevant manner in female rats, while in 250 ppm males the excreted activity of ALP and LAP from week 1 to week 18, and that of GGT during the entire study period were significantly lower than the control values. Excretion of the lysosomal enzymes aryl sulfatase A, beta-galactosidase, and beta-N-acetyl-D-glucosaminidase was at no time influenced in a noteworthy manner. Histopathology after 72 weeks revealed chronic but also acute degenerative changes in the kidneys of 250 ppm males and females. A comparison of published data on persons having undergone high cadmium exposure with the results presented here shows remarkable differences.

Biochemical response to cadmium. Dose-time effect

Dose- and time-related effects of Cd (II) (0.5 or 1.0 mg/kg, Cd as CdCl2.H2O, subcutaneously, daily for 48 h, 1, 3, or 6 wk) were investigated in rats. A dose-related increase in the activity of plasma alkaline phosphatase (ALP), lactate dehydrogenase (LDH), aspartate aminotransferase (GOT), and alanine aminotransferase (GPT) was evident only at 6 wk, whereas an early rise in ALP and LDH was seen at 3 wk in 1.0 mg Cd group only. The hepatic and renal metallothionein (MT) induction displayed a dose- as well as time-related increase with Cd accumulation. A significant increase in hepatic Zn and renal Cu, no change in hepatic Cu, and a slight increase in renal Zn was observed. Urinary ALP and leucine aminopeptidase (LAP) showed an initial increase at 48 h, thereafter returned to near normal. A second phase of enzymuria (ALP, LAP, GOT, GPT, gamma-glutamyl transpeptidase), proteinuria, and aminoaciduria occurred at 6 wk in a dose-related manner. The urinary excretion of specific renal enzymes appeared closely related to the MT induction and organ Cd levels.

Changes in urinary proximal tubule parameters in neonatal rats exposed to cadmium chloride during pregnancy

Pregnant Sprague-Dawley rats were injected intraperitoneally with physiological saline solution (vehicle) or cadmium chloride (CdCl2) at 2.0 or 2.5 mg kg-1 on days 8, 10, 12 and 14 of gestation. On postnatal day (PND) 3, 12 or 49, the offspring were examined for 8- or 24-h urinary excretion of beta 2-microglobulin (beta 2-m), metallothionein (MT) and urinary activity of three proximal tubular enzymes: gammaglutamyl transferase (GGT), alkaline phosphatase (ALP) and N-acetyl-beta-glucosaminidase (NAG). Treatment with CdCl2 did not affect growth or survival of offspring. Significant decreases in the urinary excretion of GGT, ALP and NAG were observed on PND 3, at both doses. Exposure to 4 x 2.5 mg kg-1 resulted in functional deficit of the proximal tubule on PND 3, as evidenced by the significant increase in beta 2-m. Except for a slight but significant increase of beta 2-m in 49-day-old males, all the other urinary parameters returned to control values on PND 12. There was no effect on MT. Results from this study show that prenatal exposure to CdCl2 can induce significant changes in the kidney biochemistry of rats in the early postnatal period.

The effect of chronic parenteral administration of cadmium on isoenzyme levels of alkaline phosphate in intestinal mucosa

Chronic administration of cadmium chloride to rats (13.3 mumol/kg body wt per dose subcutaneously) produced a decrease in the activity of alkaline phosphatase in the intestinal mucosa to less than half that in control rats by the time cumulative doses of between 30 and 48 mumol had been administered. The reduced level of activity remained approximately steady following further dosing. Three isoenzymes of intestinal alkaline phosphatase were separated electrophoretically. Chronic cadmium treatment markedly decreased the proportion of the 2 isoenzymes with lower electrophoretic mobility. Some analogies are drawn between the effect of cadmium administration, and magnesium deficiency on changes in intestinal alkaline phosphatase.

Urinary trehalase as an early indicator of cadmium-induced renal tubular damage in rabbit

The significance of urinary trehalase as a possible early indicator of renal disorder was examined using Cd-treated rabbits, which received 1 mg/kg Cd thrice weekly for 3 months subcutaneously. The results showed that urinary trehalase increased significantly from 1 week after treatment, earlier than LAP, ALP, proteinuria and glucosuria, with no changes in plasma trehalase level. A marked decrease in trehalase activity in renal brush border membranes prepared from Cd-treated rabbits was observed. It was also confirmed by immunohistological techniques that Cd treatment resulted in a marked decrease in specific fluorescence compared with controls. Ouchterlony double diffusion analysis demonstrated that urine and renal brush border extracts formed precipitation lines against anti-renal trehalase IgG, indicating that urinary trehalase and renal trehalase had the same antigenicity. Therefore, the facts presented here would suggest that urinary trehalase originated from the renal brush border, indicating its superiority as a diagnostic tool over other indicative indicating its superiority as a diagnostic tool over other indicative enzymes like LAP and ALP in detecting injury to renal proximal tubular cells in the early stage.

Significance of increase in urinary metallothionein of rats repeatedly exposed to cadmium

Cadmium chloride was injected subcutaneously (s.c.) into female Wistar rats at a dose of 1 mg Cd/kg body weight, 5 times a week up to 10 weeks. At specified intervals, 24-h urine was collected and the excreted amounts of metallothionein (MT), cadmium, copper, zinc and several indicators of renal damage were determined. Concentrations of cadmium and MT in the livers and kidneys of rats were also determined. Both cadmium and MT in the livers and kidneys were increased upon cadmium exposure. The urinary MT excretion started to increase within a week after the start of exposure. This increased excretion preceded those of enzymes and total protein as well as histopathological abnormalities in the proximal tubular cells. After the occurrence of tubular damage that disturbs reabsorption of MT, MT in urine was drastically increased. These results indicate that urinary MT levels may be an indicator not only of cadmium exposure but also of tubular damage.

Rat kidney brush border enzyme activity following subchronic oral lead exposure

Rats received 0.1% lead acetate in their drinking water for 3 weeks or for 6 weeks, at which time renal brush border fractions were obtained for measurement of enzyme activity. Renal brush border preparations from Pb2+-exposed rats exhibited statistically significant decreases in the activity of gamma-glutamyl transpeptidase and alanine aminopeptidase after 3 or 6 weeks of treatment. There was an increase in the activity of alkaline phosphatase which was statistically significant after 3 weeks of Pb2+ exposure. The (Na+,K+) adenosine triphosphatase activity and urokinase activity, located in the basolateral membrane fractions, were unchanged by Pb2+ exposure, as were the protein and phospholipid contents of the brush border fractions. The results are compared to those following acute exposure to Pb2+ or Cd2+.

The activity of membrane enzymes in homogenate fractions of rat kidney after administration of lead

Rats received one or two consecutive daily ip injections, each 0.5 mg Pb2+/100 g body weight, and the kidneys were studied 48 or 24 hr, respectively, after the injection. Renal brush border preparations from Pb2+-treated rats exhibited significant decreases in the activity of alanine aminopeptidase and gamma-glutamyl transpeptidase, greater after two injections, yet the amount of brush border protein remained unchanged. Moreover, the activity of alkaline phosphatase in the brush border was significantly increased after Pb2+. No significant changes in urine volume, urinary protein, or enzymes could be detected in these experiments. The enzymatic changes observed in the brush border after acute exposure to Pb2+ contrasted with those after exposure to Hg2+ where both the structure and enzymatic functions were severely damaged and after exposure to Cd2+ where enzymatic alterations were not accompanied by cytological changes.

Time-dependent protective effect of selenium against cadmium-induced nephrotoxicity and hepatotoxicity

The role of selenium in protection against nephrotoxicity and hepatotoxicity of cadmium in rats was investigated. The administration of Cd (3 mg/kg, s.c.) for 3 days enhanced the urinary excretion of lactic dehydrogenase (LDH), glutamic oxaloacetic transaminase (GOT) and total proteins, decreased the renal activity of GOT and alkaline phosphatase (ALP) and increased the renal level of Cd, Cu and Zn. Cadmium also increased the serum GOT and glutamic pyruvic transaminase (GPT), decreased the hepatic activity of GOT and GPT and increased the hepatic level of Cd and Zn. The concomitantly administered Se (2 mg/kg, i.p.) initially reduced most of these Cd-induced alterations. The results show protection by Se against nephrotoxicity and hepatotoxicity of Cd on the 4th day of the commencement of Cd administration, but the signs of Cd intoxication were observed on the 8th day.

The urinary excretion of alkaline phosphatase after the repeated parenteral administration of cadmium to rats given a high dietary supplement of zinc

Repeated parenteral administration of cadmium (Cd) (1.5 mg Cd2+/kg, daily for 28 days) produced an initial transitory (< 4 days) increase in the urinary excretion of alkaline phosphatase within 48 h: a second and persistent phase of enzymuria developed around day 15. Pretreatment and simultaneous administration of zinc (Zn) as a dietary supplement (2000 ppm Zn2+) abolished the initial phase of enzymuria but had no effect upon the second phase.