AJP - Gastrointestinal and Liver Physiology, Vol 251, Issue 1 155-G159, Copyright © 1986 by American Physiological Society
Transcellular sodium transport and intracellular sodium activities in rabbit gallbladder
W. M. Moran, R. L. Hudson and S. G. Schultz
This study was designed to explore the relation between the rate of
transcellular active Na+ transport by rabbit gallbladder epithelium, JNa,
and the intracellular Na+ activity, (Na)c; the latter was determined by use
of highly selective Na+ microelectrodes. The underlying strategy was based
on the well-established observation that JNa is stimulated by the presence
of bicarbonate in the bathing solutions. Our results confirm previous
observations that the addition of bicarbonate to the bathing solutions
results in a twofold increase in JNa. In the absence of bicarbonate, (Na)c
averaged 16 mM. Within 2-4 min after the addition of bicarbonate to both
bathing solutions, (Na)c increased to an average value of 22 mM and then
gradually declined and by 15 min did not differ significantly from the
value observed in the absence of bicarbonate. Thus, a twofold increase in
JNa is not associated with an increase in (Na)c. These results are in
accord with earlier observations on Necturus urinary bladder and small
intestine and contradict the notion that an increase in the rate of active
Na+ extrusion from the cell across the basolateral membrane in response to
an increase in the rate of Na+ entry across the apical membrane is
necessarily the result of a sustained increase in (Na)c.
