Glycogen deposition in distal tubular cells during HgCl2 induced acute renal failure

Skeletal muscle glycogen phosphorylase is irreversibly inhibited by mercury: molecular, cellular and kinetic aspects

Muscle glycogen phosphorylase (GP) plays an important role in muscle functions. Mercury has toxic effects in skeletal muscle leading to muscle weakness or cramps. However, the mechanisms underlying these toxic effects are poorly understood. We report that GP is irreversibly inhibited by inorganic (Hg(2+)) and organic (CH3Hg(+)) mercury (IC50=380 nM and kinact=600 M(-1) s(-1) for Hg(2+) and IC50=43 μM and kinact=13 M(-1) s(-1) for CH3Hg(+)) through reaction of these compounds with cysteine residues of the enzyme. Our data suggest that the irreversible inhibition of GP could represent one of the mechanisms that contribute to mercury-dependent muscle toxicity.

Early indication of effects of puromycin aminonucleoside using a fluorimetric assay of 2-aminoacridone-derivatized carbohydrates in urine

This paper describes a novel noninvasive method to study the changes in free carbohydrates excreted in urine as a result of toxicity in the rat induced by the administration of puromycin aminonucleoside (PAN). Urine samples were collected for 24 h prior to dosing and at 8, 24, and 32 h postdosing. For each sample, free carbohydrates were extracted from the urine using a graphitized carbon column and then labeled with 2-aminoacridone (2-AMAC) prior to analysis by hydrophilic interaction liquid chromatography (HILC). Dramatic changes were seen in the profile of the carbohydrates at the 8- and 24-h time points. These changes in carbohydrate profiles may be useful as early indicators of toxicity.

Rhamnus cathartica (buckthorn) hepatocellular toxicity in mice

The toxicity of the plant Rhamnus cathartica was assessed in mice after the plant was identified as a potential cause of an idiopathic neurologic disease in horses. Another member of the Rhamnaceae family, Karwinskia humboldtiana, is neurotoxic to mammals and birds and can induce hepatic degeneration and necrosis. To investigate the toxicity of R. cathartica, a 34-day feeding trial in mice was conducted using a complete rodent diet with 0, 5, or 25% added R. cathartica. No clinical signs or gross lesions were seen, and all major tissues were histologically normal except the liver. The livers of mice fed R. cathartica had marked hepatocellular swelling. Results from periodic acid-Schiff reaction staining and from electron microscopy confirmed that the swelling was due to deposits of monoparticulate glycogen (beta particles) in the cytoplasm. Glycogen deposition is an uncommon toxic change in cells. Apparently, compound(s) in R. cathartica directly or indirectly interfered with glycogen metabolism (either glycogenesis or glycogenolysis). Mechanistic and chronicity studies with R. cathartica are needed to investigate the pathophysiology of the glycogen disturbance and to determine if hepatic injury progresses and if other organs will be injured.

Evidence for intrarenal kallikrein storage during chromate-induced acute renal failure in rat

During the course of chromate-induced acute renal failure (ARF), urinary kallikrein excretion (UKE), a serine protease of distal tubule origin in the normal animal was decreased but tissue kallikrein concentration (TK) was increased, suggesting intracellular accumulation. Severe morphological lesions were observed in proximal tubular cells which showed brush border damage, numerous vesicles, necrosis and liquefaction of cytoplasmic material. Less marked changes were also present in distal tubules: large apical vacuoles and swollen mitochondria. Compared to normal rats, using the peroxidase-anti-peroxidase (PAP) method for light microscopy, greater kallikrein immunoreactivity was detected along the apical pole in distal tubules, on the membrane and in the cytoplasm as well as in the glomerulus. By immunoelectron microscopy, kallikrein was found in the connecting apical area, along the luminal, basolateral and basement membranes, in some vesicles, in Golgi apparatus and on ribosomes bound to endoplasmic reticulum. In the glomerulus, kallikrein was observed along the luminal surface of endothelial cell. After 14 days a progressive recovery of renal function, tissue morphology and UKE towards control values was observed. The presence of immunoreactive kallikrein in the glomerulus observed only during ARF confirmed the previous demonstration of kallikrein mRNA in the glomerulus. The cellular accumulation results more likely from a dysfunction of a general secretory mechanism due to cell membrane alteration than from a specific inhibition of kallikrein production and secretion.

The long-term effects of uranyl nitrate on the structure and function of the rat kidney

Studies were undertaken to determine the long-term effects of the nephrotoxin, uranyl nitrate, on the function and structure of the rat kidney. Animals were injected with 10 mg/kg B.Wt. of uranyl nitrate and renal function studies were performed one, two, four and eight weeks after drug administration. Light microscopy and scanning and transmission electron microscopy were used to characterize the morphologic changes at each time interval. Glomerular filtration rate was significantly reduced (P less than 0.01) one week (0.18 +/- 0.06 ml/min/100 gm B.Wt.) and two weeks (0.54 +/- 0.09 ml/min/100 gm B.Wt.) after drug treatment compared to controls (1.01 +/- 0.4 ml/min/100 gm B.Wt.) and returned to normal values by four weeks. The fractional excretion of sodium was significantly increased (P less than 0.01) one week after uranyl nitrate treatment (2.45% +/- 0.82) compared to controls (0.29% +/- 0.11). No further differences in this parameter were noted after one week. At all time intervals studied the pars recta of the proximal tubule (S2 and S3 segments) was the most consistently damaged region of the nephron. Acute tubular necrosis and tubular regeneration of these segments were evident one and two weeks after drug administration. Many of the tubules were widely dilated and lined by low-lying squamous epithelial cells. By four weeks some of these pars recta segments could be classified as microcysts and this type of lesion persisted as long as eight weeks after treatment. Regeneration of most injured proximal tubules was complete by eight weeks. Atrophic proximal tubules, marked interstitial fibrosis and a mononuclear cell infiltration, consistent with a chronic type of injury, were noted at the later time intervals. These results suggest that uranyl nitrate induces a persistent injury to the kidneys of rats causing lesions as long as eight weeks after injection.