Effects of aluminum on the liver following high-dose enteral administration to rats

Parenteral administration of aluminum (Al) to animals can result in hepatobiliary dysfunction, including elevated total serum bile acid concentration, reduced bile flow, and reduction of mixed function oxidase activities. Despite substantial hepatic Al accumulation, biliary Al excretion is negligible. We studied the effects of enteral administration of pharmacologic doses of Al to rats in order to see if by this route Al also produced hepatobiliary dysfunction or if biliary Al excretion was enhanced following enteral administration, protecting the liver from the effects of Al. Six rats were given 100 mg/kg/day of Al for 14 days as Al citrate by duodenal cannula. Pair-fed littermate controls were given sodium citrate. Serum Al and urinary Al/creatinine were significantly higher in Al-fed rats than in controls. Liver Al was significantly increased in the Al-fed group, but very low when compared to liver Al concentration with intravenous Al administration. Biliary Al was only 2 +/- 1% of urinary Al in the experimental group. Serum bile acid concentration and bile flow were not different between groups. We conclude that Al given in pharmacologic doses is absorbed but does not accumulate in the liver. We hypothesize that a slow rate of Al absorption may not overwhelm plasma transferrin carrying capacity or renal Al excretory capacity.

The role of aluminum in the pathogenesis of anemia in an outpatient hemodialysis population

Anemia is a well-defined complication of aluminum overload in chronic dialysis patients which may be present before other manifestations of aluminum toxicity are obvious. Causes of anemia in chronic renal failure are multiple, and at the present time there is no marker for aluminum-induced anemia. Deferoxamine (DFO) treatment can correct aluminum-related anemia and microcytosis, but may be associated with side effects. Because of the possible role of aluminum in red blood cells in causing the anemia associated with aluminum overload, we attempted to test red blood cell (RBC) aluminum as a marker for aluminum-associated anemia and to assess the prevalence of aluminum-associated anemia in an outpatient dialysis population. Both random plasma aluminum and RBC aluminum correlated well with the increase in plasma aluminum seen following DFO challenge. However, RBC aluminum was affected less by changes in oral aluminum intake than plasma aluminum. There were strong correlations of RBC and plasma aluminum to corpuscular volume (MCV) in our patients. Moreover, patients within the highest quartile of RBC aluminum had a lower mean MCV (82.1 +/- 1.7 vs 89.6 +/- 1.7, p less than .01) and hematocrit (HCT) (24.3 +/- 4 vs 28.2 +/- 1.5, p less than .05) than those within the lowest quartile. These data suggest that aluminum toxicity is an important cause of microcytic anemia in outpatient hemodialysis patients. Prospective long-term studies are needed to further define the usefulness of RBC aluminum in diagnosing and following hemodialysis patients with aluminum-induced anemia.

Rapid removal of DFO-chelated aluminum during hemodialysis using polysulfone dialyzers

Aluminum (Al) removal following deferoxamine (DFO) therapy in hemodialysis patients was evaluated in a paired-fashion comparing cuprophane (Travenol 12.11) and polysulfone (Fresenius F-80) dialyzers. QB and QD were held constant at 250 and 500 ml/min, respectively. The polysulfone dialyzer increased total plasma Al clearance from 20.0 +/- 2.8 to 80.5 +/- 7.6 ml/min (P less than 0.01), and reduced the t 1/2 of plasma Al during hemodialysis from 538 +/- 113 to 112 +/- 12 min (P less than 0.01). The polysulfone F-80 dialyzer increased Al removal during the first hour of hemodialysis from 518 +/- 191 to 1812 +/- 720 micrograms/hr (P less than 0.01). During a four hour hemodialysis the F-80 dialyzer returned plasma Al levels to pre-DFO values (103 +/- 36 vs. 93 +/- 23, P less than 0.05), suggesting complete removal of the DFO chelated Al complex. In one patient Al removal was evaluated using cuprophane, F-40, F-60 and F-80 dialyzers and the t 1/2 for Al removed decreased from 484.6 to 276.1 and 108 to 99 minutes, respectively. These data show the Fresenius F-80 polysulfone dialyzer effects the rapid removal of DFO-Al complexes. We propose use of the Fresenius F-80 dialyzer in conjunction with reduced DFO doses and i.m. administration of DFO the day prior to dialysis to limit DFO exposure as a method to decrease DFO-related side-effects in hemodialysis patients.

Aluminum-associated hepatobiliary dysfunction in rats: relationships to dosage and duration of exposure

Aluminum may contaminate parenteral nutrition solutions and accumulate in bone and liver of patients receiving this therapy. Although aluminum exposure is associated with low-turnover osteomalacia, there are few studies of hepatotoxicity. We therefore studied the effects of aluminum given to rats on total serum bile acid concentration and bile flow to determine if aluminum administration could produce abnormalities. Aluminum was given intravenously as follows: 5 mg/kg daily for 7 or 14 days and 1 mg/kg for 14 days. Hepatic aluminum was high in treated rats and undetectable in controls. Total serum bile acid concentrations were significantly higher in treated rats than in pair-fed controls with higher concentrations after 14 days than after 7 days. Bile flow was reduced by 33% in rats given 5 mg/kg but not in rats given 1 mg/kg. Hepatic aluminum correlated inversely with bile flow but not with serum bile acid concentration. Aluminum exposure in rats is associated with elevated serum bile acid concentration and diminished bile flow and may play a role in the pathogenesis of parenteral nutrition-induced hepatobiliary dysfunction.

Enhanced gastrointestinal absorption of aluminum in uremic rats

To investigate the possibility of enhanced gastrointestinal absorption of aluminum in uremia, we measured the urinary aluminum excretion of rats following an oral load of 11 mg aluminum. Rats, in which uremia had been established by the remnant kidney model, excreted 1.5 to 2.2-fold higher amounts of aluminum in their urine over a collection period of five days compared with their controls. Within this period of time up to 0.17 +/- 0.08% of the oral dose of aluminum was recovered in the urine of the uremic animals. Serum concentrations of aluminum were significantly elevated five hours after ingestion of aluminum, but this increase was similar in rats with normal or reduced renal function. Uremic rats excreted significantly less aluminum during the first 24 hours after i.v. administration of 15 micrograms aluminum if the data were corrected for the higher baseline excretion rates. The excretion rate showed a negative correlation with the serum creatinine. Selective parathyroidectomy had no effect on the pattern or amount of urinary aluminum excretion after an oral load in either uremic rats or in rats with normal renal function. We conclude that the gastrointestinal absorption of aluminum is increased in uremic rats, and that parathyroid hormone has no detectable effect on the magnitude of aluminum absorption, regardless of the renal function in this model.

Hepatic abnormalities associated with aluminum loading in piglets

Cholestasis is a common complication of total parenteral nutrition (TPN) in infants. A contributing factor to the hepatic dysfunction may be a contaminant of the TPN solution, such as aluminum, that accumulates in liver and may act as a hepatotoxin. To study the hepatic effects of aluminum, growing piglets were given daily intravenous injections of aluminum, 1.5 mg/kg, for 50 days; pair-fed controls were given heparinized saline. At sacrifice, liver and serum were obtained. Liver was analyzed for histopathology and for aluminum content and localization. The hepatocyte lysosomes of the experimental group showed aluminum peaks by x-ray microanalysis, whereas the control group did not. No differences in ultrastructure were noted between the two groups when examined by electron microscopy. Mean serum total bile acid levels (27.8 +/- 15.9 SD vs 6.3 +/- 1.5 mumol/liter, p less than 0.05), mean alkaline phosphatase (309 +/- 108 vs 180 +/- 27 IU/liter, p = NS), and mean hepatic copper content (24.8 +/- 4.5 vs 14.4 +/- micrograms/g dry weight, p less than 0.01), were elevated in the aluminum-loaded piglets, indicating that cholestasis may have been produced. Also, a small but significant reduction in serum levels of 25 hydroxy-vitamin D was found in the aluminum-loaded piglets, suggesting that vitamin D hydroxylation may be impaired. Inasmuch as lysosomal contents are excreted into the bile, aluminum accumulation in lysosomes may alter lysosomal function and possibly affect bile flow or content.

Efficacy of intramuscular and intraperitoneal deferoxamine for aluminum chelation

As intravenous administration of deferoxamine is difficult in home dialysis patients we set out to determine the efficacy of intramuscular (i.m.) and intraperitoneal (i.p.) deferoxamine for removal of aluminum. Patients with serum aluminum levels greater than 90 micrograms/liter were studied in a paired fashion with each patient serving as their own control. Serum and peritoneal fluid aluminum were determined using flameless atomic absorption. In hemodialysis patients 2 g of intravenous deferoxamine increased serum aluminum from 124.7 +/- 32.4 to 415 +/- 192.4 micrograms/liter. One g of deferoxamine given intravenously or intramuscularly resulted in 76.8 +/- 35.3% and 70.4 +/- 23.2%, respectively, of the 2 g i.v. response. The rate at which serum aluminum increased following i.v. deferoxamine infusion was biphasic, with an initial rapid phase lasting 139 minutes followed by a much slower phase. The volume of distribution of aluminum following deferoxamine administration was 12.6 +/- 1.61 and the half life (t1/2) for aluminum removal during hemodialysis was 9.0 +/- 2.0 hours. The increase in serum aluminum following deferoxamine was not due to chelation of erythrocyte aluminum as erythrocyte aluminum remained constant over 24 hours. In patients on continuous ambulatory peritoneal dialysis, 2 g intravenous deferoxamine resulted in the removal of 560 +/- 267 micrograms of aluminum over 24 hours while 2 g deferoxamine given intraperitoneally gave 91 +/- 13% of the intravenous response. Aluminum clearance over 48 hours was twice that for 24 hours for both i.v. and i.p. deferoxamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Tissue and cellular basis for impaired bone formation in aluminum-related osteomalacia in the pig

Bone formation is impaired in aluminum-associated bone disease. Reductions in the number of osteoblasts or in the function of individual osteoblasts could account for this finding. Thus, quantitative bone histology and measurements of bone formation were done at three skeletal sites in piglets given aluminum (Al) parenterally, 1.5 mg/kg per d, for 8 wk (Al, n = 4) and in control animals (C, n = 4). Bone Al was 241 +/- 40 mg/kg per dry weight in Al and 1.6 +/- 0.9 in C, P less than 0.001. All Al-treated animals developed osteomalacia with increases in osteoid seam width, osteoid volume, and mineralization lag time at each skeletal site, P less than 0.05 vs. C for all values. Mineralized bone formation at the tissue level was lower in Al than in C, P less than 0.05 for each skeletal site, due to reductions in active bone forming surface. Bone formation at the cellular level was similar in each group, however, and total osteoid production by osteoblasts did not differ in C and Al. Aluminum impairs the formation of mineralized bone in vivo by decreasing the number of active osteoblasts, and this change can be distinguished from the effect of aluminum to inhibit, either directly or indirectly, the calcification of osteoid.

Flow cytometry in feminizing adrenocortical carcinoma

A case of feminizing adrenal cortical neoplasm is presented in which automated flow cytometry determination of deoxyribonucleic acid content was used to confirm malignancy.

Evidence of aluminum loading in infants receiving intravenous therapy

To investigate the possibility that premature infants may be vulnerable to aluminum toxicity acquired through intravenous feeding, we prospectively studied plasma and urinary aluminum concentrations in 18 premature infants receiving intravenous therapy and in 8 term infants receiving no intravenous therapy. We also measured bone aluminum concentrations in autopsy specimens from 23 infants, including 6 who had received at least three weeks of intravenous therapy. Premature infants who received intravenous therapy had high plasma and urinary aluminum concentrations, as compared with normal controls: plasma aluminum, 36.78 +/- 45.30 vs. 5.17 +/- 3.1 micrograms per liter (mean +/- S.D., P less than 0.0001); urinary aluminum:creatinine ratio, 5.4 +/- 4.6 vs. 0.64 +/- 0.75 (P less than 0.01). The bone aluminum concentration was 10 times higher in infants who had received at least three weeks of intravenous therapy than in those who had received limited intravenous therapy: 20.16 +/- 13.4 vs. 1.98 +/- 1.44 mg per kilogram of dry weight (P less than 0.0001). Creatinine clearances corrected for weight did not reach expected adult values until 34 weeks of gestation. Many commonly used intravenous solutions are found to be highly contaminated with aluminum. We conclude that infants receiving intravenous therapy have aluminum loading, which is reflected in increased urinary excretion and elevated concentrations in plasma and bone. Such infants may be at high risk for aluminum intoxication secondary to increased parenteral exposure and poor renal clearance.

Hepatic aluminum accumulation in children on total parenteral nutrition

Five children receiving long-term total parenteral nutrition (TPN) containing casein hydrolysate as the protein source underwent percutaneous liver biopsies because of the development of cholestasis and abnormal liver function tests. All five demonstrated moderate to severe histopathologic changes. In addition, hepatic aluminum content was determined to be markedly elevated in all cases. Although the hepatotoxicity of aluminum is as yet undetermined, deposition of other metals has been associated with liver damage, and aluminum has been associated with pathology in other tissues. Thus, the possibility that aluminum deposition may play a role in the pathogenesis or exacerbate the course of liver dysfunction associated with TPN should be considered.

Aluminum loading in children with chronic renal failure

Plasma aluminum levels were measured in 17 children with chronic renal failure who were receiving aluminum containing antacids for the control of hyperphosphatemia. Seven children were on hemodialysis, five on peritoneal dialysis, and five were awaiting dialysis with creatinine clearances between 10 to 20 cc/min/1.73 m2. Plasma aluminum levels correlated directly with oral aluminum dosage; extremely high levels were documented in small, nondialyzed children. Bone aluminum levels were measured in four children with high plasma levels and confirmed significant aluminum loading. Other factors such as the level of aluminum in dialysate and tap water were measured and were not contributory. All patients with plasma aluminum levels greater than 100 micrograms/liter had signs of aluminum toxicity and were receiving greater than 75 mg/kg/day of elemental aluminum orally. We concluded that children who require greater than 30 mg/kg/day of elemental aluminum to control hyperphosphatemia should have plasma aluminum levels monitored and/or be considered for other forms of therapy including more restricted diets and earlier or more aggressive dialysis.

Aluminum loading during total parenteral nutrition

Patients on long-term total parenteral nutrition were found to have elevated aluminum (AI) levels in bone, and plasma, with the casein in the total parenteral nutrition solution the source of A1. Substitution of amino acids for casein was followed by a fall in urinary and plasma A1. Thus, parenteral loading with A1 increases tissue A1, particularly in bone. Whether A1 accumulation contributes to bone disease remains unclear, but the prolonged use of casein in total parenteral nutrition solutions may be inadvisable.

Bone aluminum and histomorphometric features of renal osteodystrophy

To evaluate the relationship between aluminum and the characteristics of bone disease in uremia, bone aluminum content and quantitative histomorphometric analysis of bone were evaluated in bone biopsies from 59 uremic patients undergoing maintenance hemodialysis. Biopsies were classified as showing 1) pure osteomalacia (OM) in 23 cases, 2) osteitis fibrosa (OF) in 13, 3) mixed in 7, and 4) mild lesions in 16. There were no significant differences in levels of serum calcium or alkaline phosphatase between the groups, but serum phosphorus levels were slightly higher in those with OF. Serum immunoreactive parathyroid hormone levels were greater in the patients with OF and mixed lesions than in patients with OM or mild lesions (P less than 0.01). Bone aluminum exceeded normal in all groups (P less than 0.01), with values of 175 +/- 18 mg/kg dry wt in OM patients, 46 +/- 7 of OF patients, 81 +/- 29 in mixed subjects, and 67 +/- 7 in patients with mild lesions. Bone aluminum was significantly higher in the OM patients than in any other group (P less than 0.01); also, bone aluminum correlated with the quantitative measure of unmineralized osteoid in OM (r = 0.67; P less than 0.001); no correlations existed for the other groups. There were inverse correlations between bone aluminum and the serum immunoreactive parathyroid hormone (r = -0.35; P less than 0.01) and resorbing surface on biopsy (r = -0.44; P less than 0.001). Bone aluminum correlated with the duration of hemodialysis in patients with OF with mixed and mild lesions (r = 0.49); no relation was seen in OM patients, and bone aluminum was higher for the duration of dialysis, suggesting that aluminum may accumulate more rapidly in OM subjects. These findings are consistent with but do not prove the hypothesis that aluminum plays a pathogenic role in dialysis osteomalacia; the mechanism by which aluminum accumulates remains unknown.

Histological quantitation of aluminum in iliac bone from patients with renal failure

Aluminum in undemineralized, methyl methacrylate-embedded iliac bone from 16 hemodialyzed renal patients and six normal controls was stained by a modification of the aluminon method and quantitated histomorphometrically, and the results were compared with the aluminum values measured by atomic absorption spectrophotometry. There was a high degree of correlation between the two techniques (r = 0.955, p less than 0.0001). The amount of stained aluminum also showed a statistically significant relationship with the amount of bone that is not mineralized (r = 0.840, p less than 0.001), with the TM (r = 0.841, p less than 0.001), and with osteoid width (r = 0.771, p less than 0.0001). The aluminum was found as bright red bands mainly in the junction of mineralized bone and osteoid but was also observed in cement lines of mature bone, on neutral surfaces, and surrounding the osteocytes. Analysis of serial sections for aluminum and tetracycline showed that a majority of the sites with aluminum did not take up tetracycline, implying defective mineralization. Occasionally tetracycline uptake was observed in such places, suggesting that the aluminum "block" might be overcome eventually. The presence of aluminum in cement lines of mature bone supports this hypothesis. The histochemical staining of aluminum provides a quick and easy method for identifying, localizing, and quantifying aluminum within the bone and may prove to be a useful tool in the study of the mechanisms of metabolic bone disease.

Comparison of assisted and controlled mechanical ventilation in anesthetized swine

We compared assisted mechanical ventilation with controlled mechanical ventilation with and without PEEP in 10 anesthetized swine. Catheters were placed to measure airway, intrapleural, and blood pressure; PaO2 and PaCO2; arterial pH; total minute ventilation; and mixed exhaled oxygen and carbon dioxide tensions. We calculated the ratio of physiological dead space to tidal volume, alveolar minute ventilation, CO2 production, VO2, and RQ. We found no clinically or statistically significant difference between assisted and controlled ventilation.

Extraosseous calcification. Evidence for abnormal pyrophosphate metabolism in uremia

The inorganic constituents and crystalline features of extraosseous calcium-phosphate deposits obtained from dialyzed uremic and hypercalcemic patients were studied. Visceral calcification (heart, lung, and kidney) in hypercalcemic patients exhibited either an amorphous or apatitic X-ray diffraction pattern. Uremic visceral calcification consistently gave an amorphous diffraction pattern. Although the calcium content of uremic and hypercalcemic visceral deposits was similar, other inorganic constituents were different. The mean pyrophosphate was 11 +/- 11.8 and magnesium 4.91 +/- 3.86 mg/g in the uremic group as compared to 0.92 +/- 0.24 and 1.36 +/- 1.26 mg/g in the hypercalcemic group (P less than 0.025). After incineration hypercalcemic visceral deposits having an amorphous diffraction pattern were found to generate pyrophosphate supporting the presence of brushite in these deposits. The small amount of pyrophosphate in apatitic deposits from both uremic and hypercalcemic patients actually decreased after incineration and the pyrophosphate content of uremic visceral deposits was unchanged by incineration. It is concluded that in hypercalcemic patients the initial visceral deposit is brushite which is subsequently transformed to apatite. Arterial and tumoral calcium-phosphate deposits in uremic patients were also apatite. Uremic visceral calcium-phosphate deposits are an unique mineral high in magnesium with approximately 30% of the phosphorus present as pyrophosphate. The high pyrophosphate content of these deposits could alter their crystalline structure and prevent the transformation to apatite. The infrared features, high magnesium content of the deposit, and resistance of pyrophosphate in the deposit to hydrolysis by pyrophosphatase suggests that the pyrophosphate may be deposited as the magnesium salt.

Effect of age and magnesium depletion on bone magnesium pools in rats

In vivo and in vitro studies were carried out to characterize the exchangeable bone magnesium pool and determine what effect age and magnesium depletion has on bone magnesium. A highly significant correlation was found between the size of the in vitro elutable and in vivo exchangeable bone magnesium (r=0.97). To show that the exchangeable bone magnesium was the surface-limited bone magnesium, elution studies were performed 4 h after the in vivo administration of radiomagnesium. Specific activity in the eluant was 85% of that found in the serum at time of death, suggesting that the elutable and exchangeable bone magnesium pools were largely the same pool. Bone magnesium concentration fell with increasing age. The entire fall in bone magnesium was a result of a decrease in the surface-limited fraction. Since bone crystals have been shown to enlarge with aging with resulting contraction of the surface area, this would be the most apparent explanation for this finding. During magnesium depletion, magnesium concentration in both the exchangeable and nonexchangeable pools decreased. The fractional change in the exchangeable pool was much larger than the change in total or nonexchangeable bone magnesium, suggesting that the surface-limited magnesium pool is available during magnesium depletion. The change in size of the nonexchangeable bone magnesium pool appeared to be more related to the duration of magnesium depletion than the change in serum magnesium levels. The fall in magnesium concentration in this pool is probably a consequence of continuing formation of low magnesium bone during the depletion period.

Bone magnesium pools in uremia

Bone magnesium pools were studied in vitro in bone specimens obtained from control subjects, from patients with chronic renal failure before and after renal transplantation, and in a patient with chronic hypomagnesemia. 30% of bone magnesium is in a surface limited pool present either within the hydration shell or else on the crystal surface. The larger fraction of bone magnesium was shown not to be associated with bone matrix but rather to be an integral part of the bone crystal. With incineration this pool was mobilized at the same temperature that sudden enlargement of bone crystal size occurred. It is suggested that heating causes surface calcium to displace magnesium from the apatite crystal. Both magnesium pools are increased in patients with chronic renal failure. The major factor determining magnesium concentration in bone would appear to be the serum magnesium level. Following renal transplantation, in association with the fall in serum magnesium, surface magnesium was within the normal range; whereas, residual magnesium was not different from the other urenic bones. Both magnesium pools were significantly reduced in a patient with chronic hypomagnesemia. The in vitro studies would suggest that surface magnesium should rapidly reflect changes in serum magnesium levels, whereas, the deeper magnesium pool is probably deposited at time of bone formation with mobilization being dependent upon the resorptive processes. Since magnesium can influence crystal size and stability it seems possible that excess bone magnesium may play a role in renal osteodystrophy.