Nephrology Dialysis Transplantation, Vol 14, Issue 6 1391-1397, Copyright © 1999 by Oxford University Press
N Sheerin, S Sacks and G Fogazzi
Background: Patients with gross haematuria of
glomerular origin may develop acute tubular necrosis and reversible renal
failure. Erythrocytes within the cytoplasm of proximal tubular epithelial
cells (PTECs) can be seen on examination of renal biopsies from these
patients. It is possible, therefore, that the tubular damage is a result of
cytotoxic breakdown products released during erythrocyte degradation.
Methods: to test this hypothesis, we evaluated (i) by
transmission electron microscopy, the capability of a PTEC line to
phagocytose and degrade erythrocytes in vitro; and
(ii) the effect on the viability of PTECs in vitro
both after erythrophagocytosis and after incubation with haemoglobin, free
iron or both. Results: Electron microscopic
examination of PTECs exposed to erythrocytes for 96 h showed that 22% of
PTECs contained one or more erythrocyte. These were within phagolysosomes
and showed varying stages of degradation with collapse and breakdown of the
cell membrane and invasion by cytoplasmic organelles (the so-called
haemolytic pathway of erythrocyte degradation). Despite the phagocytosis
and degradation of the erythrocytes, no cytotoxicity could be demonstrated
under the experimental conditions used. However, the presence of
haemoglobin, free iron or both in the culture medium was toxic to the
PTECs, resulting in a significant reduction in the number of viable cells
present. Conclusions: PTECs are able to phagocytose
and degrade erythrocytes, and haemoglobin and iron are toxic to proximal
tubular cells in vitro. Key
words: Acute tubular necrosis; erythrocyte degradation;
erythrophagocytosis; haemoglobin tubular toxicity; iron tubular toxicity;
proximal tubular cell culture.
ORIGINAL ARTICLES
In vitro erythrophagocytosis by renal tubular cells and tubular toxicity by haemoglobin and iron
Department of Nephrology and Transplantation, Guy's Hospital UMDS, London, UK; Corresponding author at: Divisione di Nefrologia e Dialisi, Ospedale Maggiore, IRCS, Via Commenda 15, I-20122 Milano, Italy
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