Relation between hydrogen ion secretion and oxygen uptake by gastric mucosa

Abstract

Bullfrog gastric mucosae were isolated, mounted between two glass chambers, and bathed with physiological salt solutions equilibrated with 5% CO2 and 95% O2. Oxygen consumption (qO2; measured polarographically) and acid secretion (qH+; pH stat method) were measured along with the transmucosal potential difference (p.d.) and current passing through the mucosa. Histamine (4 x 10–4 m) caused an increase in qH+ and qO2. In measurements on nine short-circuited mucosae the mean ratio for the ΔqH+/ΔqO2 was 2.1. Sodium thiocyanate (0.5–15 mm) caused a decrease in qH+ and qO2 and an increase in short-circuit current. These effects were reversible. The ratio of ΔqH+/ΔqO2 induced by thiocyanate varied from 5.0 to 12.0. Current (0.5 to 1.0 ma/cm2) passed through the mucosae, which reversed the normally observed p.d. to values between +70 and +240 mv (secretory side with respect to nutrient side in an external circuit), caused a decrease in qH+ and qO2; the average ΔqH+/ΔqO2 was approximately 13. Using either thiocyanate or electric current the ratio of the induced ΔqH+/ΔqO2 can really exceed 4.0, the electrochemical equivalent of oxygen, and thus if this extra oxygen provides the energy for the extra acid secretion these results invalidate a simple redox pump hypothesis of hydrogen ion transport by gastric mucosa.