AJP - Renal Physiology, Vol 256, Issue 5 869-F874, Copyright © 1989 by American Physiological Society
HCO3- secretion in mitochondria-rich cells is linked to an H+-ATPase
C. Fritsche, J. H. Schwartz, R. R. Heinen, R. Tietz and J. G. Kleinman
Department of Medicine, C. J. Zablocki Veterans Administration Medical Center, Milwaukee, Wisconsin.
Turtle bladder mitochondria-rich (MR) cells secrete H+ by an ATP-dependent
process. MR cells also secrete HCO3- by an energy-requiring, Cl- -dependent
process that may depend on a serosal H+-ATPase. To determine whether HCO3-
is linked to an H+-ATPase, O2 consumption was assessed in MR and granular
(G) cells exposed to H+ and HCO3- transport inhibitors alone and also with
an H+-ATPase inhibitor. MR and G cells were separated by Ficoll
density-gradient centrifugation and treated with ouabain and
4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS) to
maximally inhibit Na+ and luminal H+ transport. O2 consumption was measured
before and after cells were additionally treated with 10 microM
N-ethylmaleimide (NEM), an inhibitor of nonmitochondrial H+-ATPase. O2
consumption of MR cells fell after treatment with NEM (delta = 8.64 +/-
2.35 microliters O2.h-1.mg protein-1, P less than 0.025, n = 5). There was
no significant difference in G cells similarly treated (delta = 1.61 +/-
0.62 microliters O2.h-1.mg protein-1, P greater than 0.05, n = 5). Because
luminal H+ secretion is nearly abolished after treatment with SITS, the
decline in O2 consumption of 44.4 +/- 7.11% after addition of NEM is
probably due to inhibition of other non-mitochondrial H+-ATPases. In the
intact bladder, HCO3- secretion was reduced by 35.1% after serosal
application of NEM. Furthermore, in SITS-treated MR and G cells, ATP levels
as measured by the luciferin-luciferase assay method were not appreciably
different in the presence or absence of NEM.(ABSTRACT TRUNCATED AT 250
WORDS)
