Mechanisms of proximal proton secretion in bbm of herbivorous,
omnivorous and carnivorous species.
Duplain, Marcelle, Josette Noel, Angelica Fleser, Vladimir Marshansky,
Andr[acute]e Gougoux, and Patrick Vinay.
Nephrology Service, H[circumflex]opital Notre-Dame de Montr[acute]eal, and
Groupe de Recherche en Transport Membranaire, Universit[acute]e de Montreal,
Montreal, Qu[acute]ebec, H2L 4M1, Canada
APStracts 2:0024R, 1995.
The mechanisms of proton secretion by the proximal brush-border
membrane (BBM) were compared in carnivorous (dog), omnivorous (man,
pig, rat) and herbivorous (rabbit, hamster) species. The activity of
the proton pump (V-type bafilomycin-sensitive H+-ATPase) and of the
Na+/H+-exchanger (amiloride-sensitive quenching of acridine orange
fluorescence), the two major proton secretion mechanisms, were
measured. The enzymatic activity of the H+-ATPase activity was
measured in intact (endosomes) and solubilized (0.1% deoxycholate or
Triton X-100) BBM vesicles isolated by conventional Mg++
precipitation techniques. In all species, but not in man, the
fraction of the ATP turnover energizing the proton pump (bafilomycin
-sensitive respiration) was also measured in isolated proximal
tubules. Significant differences in acid transport mechanisms were
noted between species, the proton pump predominating in the BBM of
carnivorous and the Na+/H+-exchanger predominating in that of
herbivorous species. The fraction of respiration suppressible by
bafilomycin was also different in all the species considered. This
may indicate a different organization of proximal H+ transport
related to the species-specific menace to acid-base balance.
Received 8 June 1994; accepted in final form 22 January 1995.
APS Manuscript Number R315-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 February 1995.