Recovery of cortical phospholipidosis and necrosis after acute gentamicin loading in rats

Abstract

The recovery from gentamicin-induced phospholipidosis in the rat kidney cortex was characterized both morphologically and biochemically after a single 12-hr drug infusion. Total dosages administered were 10, 60, or 140 mg/kg, achieving constant serum concentrations of 3, 11, and 27 micrograms/ml, respectively. At the end of the 12-hr infusion, the cortical drug concentrations corresponding to the three dosages were 124, 450, and 993 micrograms/g of wet tissue. At the low dose (10 mg/kg), myeloid bodies were seen inside lysosomes of proximal tubular cells, along with a modest decrease of lysosomal sphingomyelinase activity. The cortical drug level declined steadily following first-order kinetics along with a disappearance of myeloid bodies and return of sphingomyelinase activity to control levels. At the high dose (140 mg/kg), we observed a sustained loss of sphingomyelinase activity (37% of controls), a subsequent increase of phospholipid concentration in the kidney cortex (up to 117% of controls 2 days after) and a prominent accumulation of myeloid bodies inside the lysosomes of proximal tubular cells (up to 4% of cell volume). Tubular regeneration and interstitial infiltration became detectable by histology and the increase of DNA synthesis as from day 1, along with an apparent reduction of the phospholipidosis at days 3 and 4. Drug cortical concentrations showed a sharp decline 2 days after infusion. An intermediate behavior was observed at 60 mg/kg. It is concluded that the proximal tubular cells behave in a fundamentally different way after gentamicin loading with low and high doses. At the low dose there is a regression of the drug-induced changes in the absence of any sign of necrosis-regeneration. Above a threshold in cortical drug concentration there is further development of the alterations leading to cell death-regeneration.

Uptake of Gentamicin by Bullfrog Saccular Hair Cells in vitro

“…Although gentamicin has been known to induce ototoxicity since the 1960s (Hawkins et al 1969;Wersall et al 1969), the mechanism by which it ultimately initiates hair cell death still remains unclear. Long-standing hypotheses suggest that endocytotic uptake of aminoglycosides and processing through Golgi bodies or lysosomes lead to the death of inner ear hair cells and kidney proximal tubule cells (Giuliano et al 1984;Gratacap et al 1985;Ding et al 1995;Hashino and Shero 1995;Hashino et al 1997Hashino et al , 1998Hashino et al , 2000Sandoval et al 1998Sandoval et al , 2000. However, more recent evidence suggests that aminoglycosides may access the hair cell cytoplasm via the stereociliary mechanosensory transduction channels (Gale et al 2001;Marcotti and Kros 2002).…”

Antibiotic tissue penetration and its relevance: impact of tissue penetration on infection response

“…Tissue/serum ratios for aminoglycosides are 200-fold higher in the kidneys than in nonexcretory organs (85). Although not all investigators agree, the weight of evidence favors the conclusion that these high intracellular concentrations interact with phospholipids, leading to the development of nephrotoxicity in both animal models (6,9,49) and patients (36,84). Although aminoglycosides are negligibly bound to serum proteins, binding may be interrupted by high concentrations of divalent cations (37,73).…”

Aminoglycosides Increase Intracellular Calcium Levels and ERK Activity in Proximal Tubular OK Cells Expressing the Extracellular Calcium-Sensing Receptor

“…Renal impairment, defined as an increase in plasma creatinine Ն45 mol/L during or after therapy, occurs in 10 to 37% of patients and is proportional to dose and duration of administration (1,2). Although renal failure is generally reversible, renal dialysis therapy may be required in patients with severe acute renal damage.…”

“…Nephrotoxicity has therefore been ascribed to endocytosis and sequestration of AGAs to lysosomes, formation of myeloid bodies, and phospholipidosis. Rupture of the lysosomal membrane and release of acid hydrolases follows with subsequent necrotic cell death (1,2). Central to this process is the multiligand endocytic receptor, megalin, possibly in association with cubilin, acting as the receptor for the polybasic AGAs (7,8).…”