AJP - Cell Physiology, Vol 249, Issue 5 471-C475, Copyright © 1985 by American Physiological Society
Polarity of volume-regulatory increase by Necturus gallbladder epithelium
D. J. Marsh and K. R. Spring
Necturus gallbladder epithelial cells respond to the presence of a
hypertonic perfusate in either bathing solution by first shrinking due to
osmotic water loss and then swelling back to their original volume
(volume-regulatory increase). Previous investigations involving increases
in the osmolality of the mucosal bath had suggested that volume-regulatory
increase was due to the activation of ion exchangers in the apical cell
membrane. In the present study the sidedness of the transport processes
involved in volume-regulatory increase was investigated. The osmolality of
the serosal bath was increased by 18% either in the absence of HCO3- or
when an inhibitor of volume-regulatory increase,
4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), was added to the
mucosal or serosal bath. Volume regulation was HCO3- dependent. DIDS was
only effective in inhibiting volume regulation when it was added to mucosal
bathing solution, suggesting that volume-regulatory increase depended on
transport across the apical membrane. Volume-regulatory increase could also
be activated by first swelling the cells in hypotonic solution and then
returning the tissue to control Ringer solution. The volume-regulatory
increase that occurred upon return to control Ringer was also shown to be
sensitive to DIDS in the mucosal bath.
