Effect of penicillamine on failure of renal acidification in Wilson's disease

Kidney involvement in Wilson's disease: a review of the literature

Wilson's disease (WD) is a rare inherited disease due to the mutation of the ATP7B gene, resulting in impaired hepatic copper excretion and its pathological accumulation in various organs such as the liver, the nervous system, or the kidneys. Whereas liver failure and neuropsychiatric disorders are the most common features, less is known about the renal complications. We conducted a review of the literature to define the characteristics and pathophysiology of kidney involvement during WD. This review shed light on strong evidence for direct copper toxicity to renal tubular cells. Excessive tubular copper accumulation might present with various degrees of tubular dysfunction, ranging from mild hydroelectrolytic and acid-base disorders to complete Fanconi syndrome. Proximal and distal renal tubular acidosis also favors development of nephrolithiasis, nephrocalcinosis, and bone metabolism abnormalities. Indirect complications might involve renal hypoperfusion as occurs in hepatorenal or cardiorenal syndrome, but also tubular casts' formation during acute hemolysis, rhabdomyolysis, or bile cast nephropathy. Acute kidney failure is not uncommon in severe WD patients, and independently increases mortality. Finally, specific and long-term therapy by D-penicillamin, one of the most efficient drugs in WD, can cause glomerular injuries, such as membranous nephropathy, minimal-change disease, and, rarely, severe glomerulonephritis. Altogether, our study supports the need for interdisciplinary evaluation of WD patients involving nephrologists, with regular monitoring of tubular and glomerular functions, to provide adequate prevention of renal and bone involvement.

[Multiple pseudofractures due to Fanconi's syndrome associated with Wilson's disease]

We report a 40-year-old man who presented with multiple bone pseudofractures after about 20 years from the onset of Wilson's disease (WD). At age 36, he first noticed pain in his left shoulder. At age 39, he had multiple chest pain. On neurologic examinations, dysarthria and dysphagia due to pseudobulbar palsy, rigidity and tremor on right upper lim were observed. WD was confirmed because of low levels of plasma cupper and ceruloplasmin in addition to ATP7B gene mutation. The chest X-ray revealed multiple fractures of the several ribs. We diagnosed osteomalacia due to Fanconi's syndrome because of hypophosphatemia and the impairment of renal tubules for WD. After administration of vitamin D, there happened no new bone pseudofractures. Although bone pseudofractures accompanied by Wilson's disease generally happen in childhood, we should be aware of this symptom even in adulthood.

Effects of copper on dopaminergic function in the rat corpus striatum

Copper-loading was produced in rats by administration of 0.125% CuSO4 in the drinking water for a period of 11 months from weaning. At conclusion of the treatment the animals had significant increases in liver (552%) and brain (26%) copper content relative to age-matched controls. Whereas the concentration of dopamine was unaffected, the concentration of 3,4-dihydroxyphenylacetic acid in the corpus striatum was found to be lower (25% decrease) in the copper-treated group. Saturation studies of the striatal D-2 dopamine receptors using [3H]spiperone indicated that in copper-loaded animals the affinity was significantly increased threefold, whereas there was a trend for the number of receptors to decrease. When included in the radioligand binding assay, copper salts (Cu2+) inhibited specific [3H]spiperone binding to untreated corpora striata. The inhibition produced by copper was competitive with a significant decrease in affinity, the 50% effective concentration of Cu2+ was 21 to 24 microM, and the potency of dopamine agonists was also decreased. These results are discussed in relation to the mechanism by which copper affects dopaminergic function and to the use of copper-loaded rats as a model of Wilson's disease.

Hypouricemia and hyperuricosuria as expressions of renal tubular damage in primary biliary cirrhosis

Renal tubular damage, in particular, renal tubular acidosis is associated with primary biliary cirrhosis (PBC), but hypouricemia has not been described. We studied four patients with PBC whose serum uric acid levels were 1.4 to 1.8 mg per dl, and compared their renal and liver functions with those of 11 patients with PBC whose serum uric acid levels were normal. In the patients with PBC and hypouricemia, uric acid clearance (Cua) and the ratio of Cua and creatinine clearance (Cua/Ccr) were high enough to cause hypouricemia. Elevated Cua/Ccr was suppressed by administration of pyrazinamide, a blocker of tubular secretion of uric acid, but was not affected by probenecid; the effects of drugs on Cua/Ccr were similar to those reported in Wilson's disease. Elevation in Cua/Ccr was associated with increased serum bilirubin and urinary copper excretion. These observations indicate that hypouricemia and hyperuricosuria, which may be caused by defective postsecretory reabsorption of uric acid, are additional indicators of renal tubular damage in PBC.

Acid dissociation and metal complex formation constants of penicillamine, cysteine, and antiarthritic gold complexes at simulated biological conditions

Ionization constants for acid functions of D-penicillamine, L-cysteine, thiomalic acid, and thioglucose were measured by pH titration at 37 degrees and 0.15 M ionic strength. Chelate formation constants for these ligands with calcium(II), iron(III), and gold(I) were then determined under the same conditions chosen to approximate the in vivo situation. Only iron(III) formed both 1:1 and 1:2 chelates with D-penicillamine, L-cysteine, and thiomalate; calcium formed weak and gold strong 1:1 complexes with all ligands studied. Because of precipitate formation, the stability constants for the systems thioglucose-iron(III), D-penicillamine-gold(I), and L-cysteine-gold(I) had to be determined indirectly with thiomalic acid as the competing ligand. The in vivo fate of antiarthritic gold(I) compounds remained uncertain, but gold(I) chelates probably persist as such for extended periods.

Effect of treatment on renal function in severe osteomalacia due to Wilson's disease

A patient with Wilson's disease presented at the age of 41 with a neurological defect and gross osteomalacia secondary to a defect of renal tubular reabsorption. He also showed the unusual features of a renal stone in the presence of the Fanconi syndrome and a relatively low alkaline phosphatase level, possibly due to the additional inherited defect of hypophosphatasia. During four years of treatment with penicillamine and calciferol clinical improvement was spectacular. Details of amino-acid clearances before and after treatment are given, and the results suggest that, as in the brain and the liver, the function of the distal renal tubules may be restored in Wilson's disease when copper is removed.