Active ion transport by isolated gastric mucosae of rat and guinea pig

The effects of ion substitution, inhibitors and variations in transmural p.d. on the movements of sodium and chloride across an in vitro preparation of rat gastric mucosa have been studied. The tissue maintained net steady‐state transport of sodium in the mucosal‐to‐serosal direction in the absence of transmural gradients of electrochemical potential. Sodium transport was independent of the presence of chloride, and was abolished by 1 X 10(‐5) M‐amiloride. The inhibitor produced a decrease in short‐circuit current equivalent to the depression of sodium transport, indicating that the sodium transport process was electrogenic. Variations in transmural p.d. showed that the sodium transport process included two components: one that varied with p.d. and one that was independent of it. These findings have been interpreted in terms of a system for sodium transport composed of three components: two rate‐limiting entry mechanisms at the apical membrane, one of which can be represented as a conductive channel for sodium diffusion and the other as a neutral process possibly a sodium‐hydrogen exchanger, and a voltage‐independent pump at the basolateral membrane analogous to the constant‐current pump models described in some other epithelia. The tissue maintained a net secretory movement of chloride in the short‐circuited condition. The process responsible for net transport of chloride could be resolved into two components: one that was sodium dependent, electrogenic, and abolished by 8 X 10(‐3) M‐acetazolamide, and one that was independent of the presence of sodium, electrically silent and abolished by 5 X 10(‐4) M‐SITS (4‐acetamido‐4'‐isothiocyano‐2,2'‐disulphonic acid stilbene). Both components of the chloride transport process varied with p.d. These findings were interpreted in terms of a system of three components: two entry mechanisms at the basolateral membrane including a coupled sodium‐chloride influx process and a chloride‐bicarbonate exchanger in parallel, and a rate‐limiting conductive channel at the apical membrane. In addition, the studies on the effects of variations in transmural p.d. on chloride fluxes revealed a symmetrical voltage‐independent component, dependent on the presence of chloride in the trans compartment, and it was suggested that this component may reflect the presence of a chloride‐chloride exchange mechanism.

Section: Discussionsupporting

confidence: 91%

Transport of sodium and chloride across rat gastric mucosa in vitro.

Jackson¹,

Norris²

1985

“…The present findings for isolated gastric mucosae of the adult rat confirm four previously reported observations (Sernka & Hogben, 1969;Jackson & Norris, 1985) to the effect that (1) these mucosae maintain a net steady-state transport of sodium in the mucosal to serosal direction, in the absence of transmural gradients of electrochemical potential; (2) this sodium transport is abolished by 10 pM-amiloride, which inhibits short-circuit current and sodium transport to the same degree, thus indicating that the sodium transport process is electrogenic; (3) the variations in the transmural PD indicate that the sodium transport process includes two components: one that depends on the PD and one that does not, and (4) under short-circuit conditions, adult rat stomach secretes a constant net chloride flux.…”

Section: Discussionsupporting

confidence: 93%

“…Previous studies have established that in the absence of transmural gradients of the electrochemical potential, net steady-state mucosal-to-serosal absorption of sodium and serosal-to-mucosal secretion of chloride occur across the isolated gastric mucosa of the adult rat (Kitahara, Fox & Hogben, 1969;Sernka & Hogben, 1969;Jackson & Norris, 1985). Jackson & Norris (1985) recently showed that when this mucosa was isolated in an Ussing chamber, the sodium transport process included two components; one that varies with the transmural voltage and one that is independent of this voltage.…”

Section: Introductionmentioning

confidence: 99%

Development of sodium and chloride transport across fetal and newborn rat stomach in vitro.

Ducroc

Garzon

Geloso

et al. 1988

3. However, on fetal day 20, neutral absorption of NaCl was no longer observed but amiloride had inhibited electrogenic absorption of Na+, and significant active secretion of Cl-was observed (J" = -1-3 + 0-6 pequiv cm-2 h-1). On day 21 (i.e. 24 h before birth), values for JNa )Jclt, and Is were not different from those determined on adult gastric mucosa.4. After birth, NaCl transport continued to exhibit its prenatal characteristics on day 5 but not on day 12, when Na+ and Cl-were both absorbed; on that day, jNa -I was equal to both Jclt and to the amiloride-insensitive component of Isc, indicating that neutral NaCl absorption had resumed.5. These data show that in rat stomach, NaCl transport differentiates on fetal day 20, when H+ secretion is first observed, and thereafter undergoes biphasic development.6. The significant Cl-absorption observed on post-natal day 12 was concomitant with the inhibition of net H+ secretion.

“…Such isolated mammalian stomachs have also been shown to secrete acid at low but sustained rates of 1-2 Ptequiv/cm2. hr (Cummins & Vaughan, 1965;Kitahara et al 1969;Sernka & Hogben, 1969). However, these preparations could not be stimulated by secretagogues, thus it was not possible to study the interrelationships of the electrical and flux data with gastric H+ secretary function.…”

Section: Introductionmentioning

confidence: 99%

Transport and electrical phenomena in resting and secreting piglet gastric mucosa.

Forte¹,

Machen²

1975

SUMMARY1. Gastric mucosae were isolated from piglets (0-5 days old) and mounted in a chamber where electrical properties and secretary function could be measured. Unlike many previously reported mammalian in vitro preparations, pig gastric mucosae were stable and physiologically responsive for many hours after isolation. Cl-(60-65%) and Na+ (10-15 %). The partial conductance of H+ was extremely low. The observed increase in tissue conductance associated with H+ secretary activity and the changes in the long-time constant p.d. transient to a current pulse are discussed in terms of the relative contribution of the serosal and mucosal plasma membrane surfaces.