Unique acid-base parameters of gastric venous blood during secretory activity

Recent advances in the molecular and functional characterization of acid/base and electrolyte transporters in the basolateral membranes of gastric and duodenal epithelial cells

“…Kidder & Montgomery (1974) found that physiological CO 2 tensions are not sufficient for maximal acid secretion. Eichenholz et al (1967) noticed that when acid secretion was stimulated in anaesthetized dogs, the increase in plasma HCO 3 ) in the venous blood was higher than that expected by CO 2 hydration from arterial blood CO 2 and metabolic CO production of the gastric mucosa. And while carbonic anhydrase inhibition did inhibit acid secretion (McGowan et al 1952), some researchers found that Cl ) secretion was more affected than proton secretion (Hogben 1955), while others related to effects to systemic acid-base balance rather than inhibition of parietal cell CO 2 hydration (Janowitz et al 1957, Hersey & High 1971.…”

A gastric acid secretion model

“…Although this was a curve-fit to this particular data, it is still instructive, because it predicts that the oxyntic cell must increase its uptake of K+ from the blood with its secretion rate. However, the ouabain-sensitive basolateral Na+/K+ ATPase pump is usually regarded as being regulated to keep the cell Makhlouf et al (1966) 1.01 ml/min (with saliva) Guyton (1986) or Davenport (1966) Eichenholz et al (1967) qa(Le -Lp) Cl /HCO3 exchange coefficient 8.4 x 10 2.3 mEq/h Flemstrom (1987) mEq/h per (mEqAliter)2 (calculated from T + 0.4 mEq/h Engel et al (1984) QdBd; see text)…”

“…An argument in favor of this approximation is that if diffusion out of the stomach and into the blood were rapid then the high PCO2 gradients observed between lumen and blood would dissipate in the steady-state. 3) But gas exchange between the parietal cell and the blood should be as rapid as possible to satisfy the high metabolic needs of the ATPase H+/K+ pump, and while CO2 diffusion is undoubtedly low across the mucus lining, (Ds -X00 and De -* 0) it would be advantageous for the parietal cell (via Dm) to utilize CO2 in the lumen to make H+ and HCOQ, since the CO2 supply available due to metabolism and arterial supply might be inadequate (Miyagi et al, 1966;Eichenholz et al, 1967). 4) But since Dm includes the distance into the pit and the relatively small surface area of the pit, it is better to assume that Dm -0 rather than De -* 0 because of the large area represented by surface epithelial cells.…”