Tubular Injury and Regeneration in the Rat Kidney Following Acute Exposure to Gentamicin: A Time-Course Study

Abstract

Aminoglycoside antibiotics act as nephrotoxic drugs, inducing a lysosomal phospholipidosis and necrotic lesions essentially in convoluted proximal tubules. Previous studies have demonstrated that tubular injury caused by these compounds elicits a process of renal tissue repair (tubular regeneration) involving an increase of cell turnover in tubular epithelium. The present study was performed in order to: (i) achieve further insight into the temporal relationship between aminoglycoside-induced phospholipidosis, tubular necrosis, and tubular regeneration; and (ii) approach the control of tubular regeneration after nephrotoxin-induced insult. To investigate the latter point, we examined by immunocytochemistry the intrarenal distribution of epidermal growth factor (EGF) during tubular regeneration. Five groups of female Sprague-Dawley rats (n = 5) were treated for 4 days with gentamicin i.p. at a daily dose of 50 mg/kg delivered in 2 injections per day. Sham-treated animals (n = 5) received an equivalent amount of vehicle (0.9% NaCl) according to the same protocol. Groups of treated rats, and controls, were terminated 16 h (day 1), 4 days, 7 days, 14 days, and 21 days after the end of gentamicin administration. One hour prior to necropsy, each animal was given an i.p. injection of 40 mg 5-bromo-2'-deoxyuridine (BrdU) for the immunocytochemical demonstration of S-phase cells, using an anti-BrdU monoclonal antibody. Renal tissue was processed for light microscopy analysis, namely: a computer-aided morphometry of lysosomes in proximal tubular cells, a single-blind evaluation of gentamicin-induced tubular injury, the measurement of cell proliferation by immunocytochemical detection of BrdU-labeled nuclei, the demonstration of EGF-like immunoreactive material in renal tissue by using anti-rat EGF antiserum and immunogold-silver staining. As revealed by the morphometry of lysosomes in proximal tubular epithelium, the degree of gentamicin-induced phospholipidosis was maximum at day 1 (relative area occupied by lysosomes was increased 25-fold over mean control value) and declined thereafter. In contrast, tubular necrosis reached a peak 4 days after the end of drug administration. In proximal tubular epithelium, the stimulation of cell turnover associated with tubular regeneration showed a peak at day 7 (15-fold the mean control value). Tubular regeneration was also accompanied by mild interstitial hyperplasia. Three weeks after treatment with gentamicin, morphological evidence of drug-induced injury had disappeared due to the tissue repair process, except for the occasional presence of small hyperplastic foci in renal cortex interstitium. In both treated animals and controls, EGF immunoreactivity as revealed by immunocytochemical staining was associated with distal tubules (renal cortex and outer medulla).(ABSTRACT TRUNCATED AT 400 WORDS)

Gentamicin nephrotoxicity in animals: current knowledge and future perspectives

“…The drug is then transported to lysosomes, Goldzi apparatus and endoplasmic reticulum (Silverblatt, 1982[82]). Gentamicin binds to membrane phospholipids, alters its function and lead to a condition known as phospholipidosis in humans (De Broe et al, 1984[16]) and experimental animals (Nonclercq et al, 1992[58]). Lysosomal phospholipidosis is caused by: disorder in phosphatidylinositol signaling pathway (Ramsammy et al, 1988[65]), reduced turnover of phospholipids and their accumulation in plasma membrane (Laurent et al, 1982[40]), decrease in the available negative charge for proper function of phospholipases (Mingeot-Leclercq et al, 1995[50]), inhibition of calcium dependent phosphodiesterases (Van Rooijen and Agranoff, 1985[90]) and by inhibition of phospholipases A1, A2 and C1 (Abdel-Gayoum et al, 1993[1]).…”

In Situ Demonstration of Germinal Cell Apoptosis during Diethylstilbestrol-Induced Testis Regression in Adult Male Syrian Hamsters1

“…Proliferating cells were revealed by immunodetection of BrdU incorporated into DNA as described in previous publications [29,30]. Briefly, after dewaxing and rehydration, sections obtained from tissue fixed in Duboscq-Brazil mixture were pretreated with trypsin followed by 1-h incubation at 60°C in 3 M HC1.…”

Uptake of fluorescent gentamicin by vertebrate sensory cells in vivo

“…In mammals, including humans, ototoxicity is a serious, and mostly permanent, side-effect of aminoglycoside therapy, whereas nephrotoxicity is often acute and reversible. Kidney tubule epithelia retain their ability to undergo cellular proliferation following aminoglycoside toxicity, unlike sensory epithelia in the mammalian inner ear (Chen and Segil, 1999;Nonclercq et al, 1992;Xie et al, 2001). …”