AJP - Renal Physiology, Vol 260, Issue 3 443-F458, Copyright © 1991 by American Physiological Society
Carbonic anhydrase and proton secretion in turtle bladder mitochondrial-rich cells
C. Fritsche, J. G. Kleinman, J. L. Bain, R. R. Heinen and D. A. Riley
Department of Medicine, C.J. Zablocki Veterans Administration Medical Center, Milwaukee, Wisconsin.
Bladders from actively feeding turtles were processed for carbonic
anhydrase (CA) cytochemically. CA-positive cells were identified as
microplicated (MP) cells, microvillated (MV) cells, and subluminal (SL)
cells. After acute enhancement of H+ secretion with 5% CO2, MP cells
displayed extensive microplicae and a reduced density of apical
subplasmalemmal vesicles, and they were CA reactive throughout a large part
of the cytoplasm including the microplicae. After acute inhibition of H+
secretion with a pH 4.5 mucosal bath, CA staining was excluded from the
microplicae and apical subplasmalemmal region of most MP cells, whereas
microplicae varied from extensive to reduced, and subapical vesicle density
remained elevated. MV cells were characterized by basolateral staining with
sparing of the MV and apical subplasmalemmal region in all settings except
1) after 5% CO2 and 2) when MV cells were found in areas in which MP cells
were stained to the lumen. These results indicate that CA is active at the
site of H+ secretion in MP cells and is correlated with the acute acid-base
status of the bladder.
