Role of apoptotic and nonapoptotic cell death in the removal of
intercalated cells from the medullary collecting duct of the
developing rat kidney.
Kim, Jin, Jung-Ho Cha, C. Craig Tisher, and Kirsten M. Madsen.
Department of Anatomy, Catholic University Medical College, Seoul,
Korea; and Laboratory of Experimental Morphology, Division of
Nephrology, Hypertension and Transplantation, University of Florida
College of Medicine, Gainesville, Florida 32610-0224
APStracts 2:0186F, 1995.
In the developing rat kidney, both type A and type B intercalated
cells are present throughout the medullary collecting duct (MCD) as
well as the papillary surface epithelium. After birth intercalated
cells gradually disappear from the papillary surface epithelium and
the terminal MCD and type B cells disappear from the entire MCD. The
purpose of this study was to establish the mechanism(s) by which
intercalated cells are deleted from the MCD during development and to
determine if apoptosis plays a role in this process. Kidneys from 14,
16, 18, and 20 day-old fetuses, and 1, 3, 7, and 14 day-old pups were
preserved for light microscopic immunohistochemistry and transmission
electron microscopy. Intercalated cells were identified by
immunostaining for H+-ATPase and band 3 protein. Apoptosis was
identified by nick end labeling of DNA fragments using the ApopTag
kit, staining with the vital dye toluidine blue, and transmission
electron microscopy. Two distinct mechanisms of elimination of
intercalated cells were detected. Cells with apical labeling for H+
-ATPase and basolateral labeling for band 3 protein protruded into the
lumen of the MCD as if they were being extruded from the epithelium
and many had lost contact with the basement membrane. Extrusion of
cells with basolateral H+-ATPase or with no labeling for H+-ATPase
was never observed. Apoptosis was observed in the MCD from shortly
before birth to 7 days after birth, gradually progressing from the
papillary tip towards the outer medulla. Staining for apoptosis was
present in H+-ATPase-positive apoptotic bodies, located in cells that
were negative for H+-ATPase. Staining was also occasionally observed
in apoptotic cells with basolateral H+-ATPase, but never in cells
with apical H+-ATPase. Electron microscopy confirmed the presence of
apoptotic intercalated cells in the MCD and demonstrated that
apoptotic bodies were located in IMCD cells and principal cells.
These results demonstrate that intercalated cells are deleted from
the MCD by two distinct mechanisms, one involving simple extrusion
from the epithelium, the other involving apoptosis and subsequent
phagocytosis by neighbouring principal cells or IMCD cells.
Elimination by extrusion affects only type A intercalated cells,
while deletion by apoptosis appears to occur only in type B
intercalated cells.
Received 30 March 1995; accepted in final form 27 September 1995.
APS Manuscript Number F108-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95