engleski

Actin filaments and microtubules along the rat nephron in experimental cisplatin nephrotoxicity

Cisplatin (cPt) causes nephrotoxicity with a hypoosmotic polyuria that develops in two peaks: the early peak occurs one day (D1), whereas the late peak occurs 5 days (D5) after drug administration. Some toxic heavy metals can damage the cytoskeleton and interfere with targeting of various transporters to the cell membrane, causing functional disorders. In studies in vitro, cPt affects polymerization of actin filaments and microtubules. Its possible effect on cytoskeleton in the nephron cells in vivo has not been reported. In this work we studied the abundance of actin (ACT) and  -tubulin (TUB) in tissue homogenates from the kidney cortex (C), outer stripe (OS), and inner stripe+inner medulla (ISIM) by immunoblotting, and the distribution of ACT filaments and microtubules in tissue cryosections by immunofluorescence (IF) in Wistar rats on D1 and D5 after a single i.p. dose of cPt (5 mg/kg b.m.) or 0.9% NaCl (controls). On D1 in cPt-treated rats, in comparison with controls the abundance of ACT (42 kDa band) in the C and OS remained unchanged, whereas in the ISIM, it was lower by 38%. As seen by IF, the distribution and the intensity of ACT staining in the C, OS, and IS remained unchanged, but it decreased in the IM interstitium. The abundance of TUB (55 kDa band) remained unchanged in all the tissue zones, but its IF staining was enhanced in the OS, suggesting a cPt-induced hyperpolymerization. On D5, the abundance of ACT in tissue homogenates increased 85% (C), 18-fold (OS), and 89% (ISIM). In IF studies, ACT was diminished in the C convoluted tubules. In the OS, the brush-border of the S3 segment was largely lost, ACT was redistributed to the cell periphery, indicating a loss of cell polarity, and its staining intensity dramatically increased. A similar staining pattern was observed in the tubules of IS and IM. The abundance of TUB in tissue homogenates increased slightly in the C and strongly (6-fold) in the OS, and remained unchanged in the ISIM. The IF staining showed that microtubules in the C tubules were not affected by cPt. In the S3 segment, microtubules were deranged, their staining was strongly enhanced, and numerous mitotic spindles indicated an active regeneration. The staining pattern of microtubules in the IS and IM was unchanged. The data indicate that cPt can interfere with the cytoskeleton in the nephron cells in vivo, which may damage the cell polarity and result in various functional defects, including impaired reabsorption of water.

heavy metals; immunocytochemistry; kidney

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