Weak acid accumulation in the serosal extracellular compartment of the frog gastric mucosa.

The dimethyloxazolidine dione distribution in the extracellular compartments of the frog gastric mucosa was analyzed by washout kinetics. The volumes of the two extracellular compartments, serosal and mucosal, were estimated by inulin washout as 0.435 +/- 0.019 and 0.176 +/- 0.018 microliter/microliter tissue water, respectively. In the serosal extracellular space, significant dimethyloxazolidine dione accumulations of 2.63 +/- 0.25, 2.28 +/- 0.16, and 1.86 +/- 0.08 times that of the bathing media were found for bathing solutions with pH values of 6.9, 7.4, and 7.9 respectively. A high pH of the serosal extracellular fluid by itself could not account for the high values of dimethyloxazolidine dione accumulation. A difference in the total dimethyloxazolidine dione accumulation requires: (a) the existence of differences in the pH values and also the existence of a difference in the diffusion coefficient of the two forms of dimethyloxazolidine dione; or (b), a binding of one of the two forms, i.e., binding of dimethyloxazolidine dione form by fixed charges.     

Water flow through frog gastric mucosa

To elucidate the role of protein synthesis in DNA formation, E. coli R2 infected with phage T2 was studed as a model, employing chloramphenicol to inhibit protein synthesis. The following results were obtained. 1. Chloramphenicol inhibited protein synthesis but not synthesis of nucleic acids in uninfected bacteria. 2. Studies of the effect of chloramphenicol on phage maturation indicated a delay of 2 minutes between time of addition and cessation of phage growth. 3. The increase of DNA in phage-infected bacteria was completely suppressed by the addition of chloramphenicol within 2 minutes following infection. Addition at later times showed progressively less inhibitory action depending upon the time interval, and addition after the 10th or 12th minute showed no appreciable effect on DNA synthesis despite the cessation of intracellular phage formation and protein synthesis. 4. When chloramphenicol was added to infected cells the increase of resistance to UV stopped within 2 minutes, whether or not DNA synthesis continued. Thus evolution of resistance paralleled the rate of DNA synthesis achieved, but not the amount of DNA accumulated. 5. We conclude that in infected bacteria, protein synthesis is necessary to initiate DNA synthesis but is not essential for its continuation. The resistance to UV that characterizes infected cells near the midpoint of the latent period is not due to accumulation of DNA, but depends on some chloramphenicol-sensitive process (probably protein synthesis) completed at about the time the rate of DNA synthesis becomes maximal.     

Immediate short-time effects of ethacrynic acid on frog gastric mucosa in chloride-free solutions.

The presence of ethacrynic acid in the nutrient sulphate solution produces, generally in less than 3 min, a decrease in resistance accompanied by an increase in transmucosal PD. These results strongly suggest that the dominant effect of ethacrynic acid is not on the Na+ pathway of the nutrient membrane, but without further knowledge of the resistance of other ionic pathways, it cannot be inferred whether the effect predominates on the K+ pathway as in Cl- media.     

Increase of intracellular pH in secreting frog gastric mucosa

A method of estimation of pH in frog gastric mucosa by measuring the apparent creatine kinase equilibrium was studied. In a resting, in vitro preparation of frog stomach the intracellular pH was found to increase linearly with an increase in the serosal pH. This increase was also accompanied by an increase in the apparent equilibrium constant of the creatine kinase reaction. A similar increase was found when the resting mucosa was stimulated with histamine plus theophylline. During this procedure the total content of adenine nucleotides and creatine plus creatine phosphate remained constant.     

Effects of ouabain on frog gastric mucosa in vitro

The effect of the addition of ouabain to the nutrient solution was determined on resistance, potential difference (p.d.) and H⁺ secretion rate. In NaCl media, 10^?3 M ouabain decreased significantly the p.d. from 25.6 mV to 16.1 mV in 30 min and to 11.0 mV in 60 min. NO significant changes occurred in resistance and H⁺ secretion rate. In Na₂SO₄ (Cl^?-free) media, ouabain produced a biphasic effect on p.d. The p.d. changed from ?28.0 mV (nutrient-negative) to a nadir of ?37.4 mV in 7 min and then increased to ?16.4 mV in 60 min. At the nadir there was no significant change in resistance or H⁺ secretion rate but at 60 min, unlike Cl^? media, resistance increased by 36% and H⁺ secretion rate decreased by 43%. To decide whether the ouabain-caused decrease in H⁺ rate in Na₂SO₄ media was due to an effect on the H⁺ pump or on resistance of the return pathways, the voltage was clamped at 0 and 40 mV. Clamping the voltage showed that in the case of a marked decrease in the H⁺ secretion rate, the H⁺ transport mechanism itself was inhibited (and not the parallel pathway). The decrease in p.d. due to ouabain in Cl^? and SO₄^2? media indicates that the (Na⁺ + K⁺)-ATPase mechanism may be electrogenic.     

The action of amytal on frog gastric mucosa

The frog gastric mucosa has been shown to be sensitive to amytal. At 2 mM acid secretion was completely inhibited with a rise of resistance, fall in short-circuit current and no significant change in potential difference. Simultaneously there was 75% inhibition of O₂ consumption and 50% depression of ATP levels. Dual-beam spectrophotometric studies of intact mucosa with amytal showed a crossover point between NAD⁺ and FAD. The microsomal NADH oxidase ferricyanide reductase has also been shown to be amytal sensitive. Cl⁻ transport was relatively insensitive to amytal, suggesting a qualitative distinction between the mechanisms underlying the transport of H⁺ and Cl⁻ in the mucosa. This was further brought out by the effects of anoxia in which H⁺ transport was inhibited at 5 min but Cl⁻ transport at minimally 20 min following the onset of anoxia.     

Influence of amytal and menadione on high-energy phosphates and acid secretion in frog gastric mucosa

Measurement of ATP and creatine phosphate in isolated frog gastric mucosa showed that amytal depressed the level of both high-energy compounds and inhibited acid secretion. Addition of menadione restored the ATP level to control values and partially restored the creatine phosphate levels but did not support acid secretion. Menadione was found to support that portion of active chloride transport which is not associated with acid output. It is concluded that an amytal-sensitive reaction, presumably mitochondrial coupling site I, is required for acid secretion to occur and that ATP is not a sufficient source of energy for this secretory process.