AJP - Gastrointestinal and Liver Physiology, Vol 242, Issue 4 388-G399, Copyright © 1982 by American Physiological Society
Ionic requirements for H+ secretion and membrane elaboration in frog oxyntic cells
C. D. Logsdon and T. E. Machen
We have tested whether the ions K+, Na+, or Cl- are required for either
initiation or maintenance of secretory parameters of amphibian oxyntic
cells. In vitro mucosal preparations were washed repeatedly in Ringer
solution lacking the ion in question either before (i.e., resting tissues)
or after addition of stimulants. Electrophysiology, H+ secretion, and
morphology (morphometric analysis of oxyntic cells) were monitored. Na+ or
K+. Stimulation of resting tissues in Na+ or K+-free solutions elicited no
H+ secretion; there was only a small increase (approximately twofold) in
secretory surface density (Sv) (during control Sv increased sixfold). The
Na+-free effects were partially reversed by high [K+]. In secreting
tissues, Na+ or K+-free solutions caused H+ secretion to decrease to zero.
Gastric glands from these mucosae appeared "occluded": the gland lumen was
filled with apposed apical projections of oxyntic cells. Cl-. Stimulation
after Cl- removal initiated low levels of H+ secretion. Morphologically the
cells either appeared normally stimulated (Sv increased eightfold) or, more
rarely, took on the occluded appearance. Cl- removal from stimulated
mucosae decreased H+ secretion approximately 50%, but the cells were
normally elaborate. We conclude that K+ is required for the initiation of
H+ secretion and the stimulated morphology change; the effects of Na+
removal are due to effects on internal [K+]; Cl- is not required. The
occurrence of occluded morphology under conditions of inhibited H+ and H2O
secretion indicates a role for water flow in the maintenance of stimulated
morphology.
