The Absorption of Bicarbonate‐saline Solutions by the Small Intestine and Colon of the White Rat

Parsons, D. S.

doi:10.1113/expphysiol.1956.sp001212

Cited by 110 publications

(78 citation statements)

References 4 publications

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“…The secretion of bicarbonate ions by the colon has been demonstrated in several species (Parsons, Powell & Pyrah, 1952;D'Agostino, Leadbetter & Schwartz, 1953;Parsons, 1956) and some evidence for active transport of the ion was produced by Cooperstein & Brockman (1958). The present experiments did not allow assessment of the latter possibility but did demonstrate that none of the variations produced by Na depletion affected the secretion rate.…”

Section: Ionic Fluxesmentioning

confidence: 35%

Transport of sodium and secretion of potassium and bicarbonate by the colon of normal and sodium‐depleted rats

Edmonds¹

1967

The Journal of Physiology

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SUMMARY1. Ascending and descending colonic segments of normal and Nadepleted rats were perfused in vivo with isotonic solutions of varying Na concentration and the unidirectional Na fluxes and secretion rate of K and bicarbonate and the transmucosal electrical p.d. were measured.2. Potential difference was greater in Na-depleted rats, especially towards the distal end of the descending colon. With reduction of luminal Na concentration, p.d. was reduced.3. The ascending and descending segments were similar in regard to Na transport except that the latter had lower passive permeability. Na depletion caused an increase of Na influx rate, Na net flux rate and Na exchange diffusion whilst the mucosal passive Na permeability decreased. These changes resulted in a reduction in the critical luminal Na concentration, i.e. the concentration at which the unidirectional fluxes were equal.4. K secretion rate was similar in the ascending and descending colon and was increased by Na depletion. In all rats, it was reduced when the luminal Na concentration was low.5. Bicarbonate secretion rate was unaffected by the Na depletion and all solutions remained isotonic during perfusion.6. The results confirmed that active Na transport was stimulated by Na depletion but indicated that this was probably not the only factor in the elevation of transmucosal p.d.

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Section: Ionic Fluxesmentioning

confidence: 35%

Transport of sodium and secretion of potassium and bicarbonate by the colon of normal and sodium‐depleted rats

Edmonds¹

1967

The Journal of Physiology

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“…Parsons [1956] has suggested that part of the sodium absorption in the intestine may take place through a sodium-hydrogen ionic exchange, and it might be surmised that such a process would be inhibited by increasing the H+ concentration. A comparable finding in the case of sodium is that of Schoffeniels [1955], who has shown clearly that both the influx and net transport of Na ions across frog skin are dependent upon the pH of the bathing solution on either side, both the net transport and the inward flux being reduced in the presence of increasing H-ion concentrations.…”

Section: Discussionmentioning

confidence: 99%

The Absorption of Water and Salt From the Small Intestine of the Rat

McHardy

Parsons

1957

Exp Physiol

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WE have previously reported the results of experiments on the absorption of inorganic phosphate from the small intestine of the rat under controlled conditions [McHardy and Parsons, 1956]. During these experiments the net absorption rates of water and some electrolytes were also measured and these findings are described in this paper. METHODSThe experimental technique and the methods of determining the phosphate concenrtration, pH and tonicity of the fluid circulating in the intestinal segment have been described previously [McHardy and Parsons, 1956].Analyses.-Sodium and potassium were estimated with a directreading flame photometer [Parsons and Cox, unpublished] and chloride by the method of Sendroy [1937]. Glucose was estimated by the method of Hulme and Narain [1931], and urea by the Kjeldahl procedure on protein-free filtrates of the circulating fluid. At the end of each experiment the circulated segment was removed from the animal and its length and wet weight were measured; after six hours drying in an oven at 105°-10°C. the dry weight was measured and the water content found by subtraction. At the end of certain experiments blood was taken from the heart with anaerobic precautions and the plasma obtained was used for electrolyte determinations.Calculation and Expression of Results.-In calculating the absorption rate of water, phosphate was used as a "volume indicator" as described for sugars by Fullerton and Parsons [1956], the initial and final volume of circulating fluid being determined from the initial and final phosphate content and concentration. The absorption rates of the various solutes were calculated from the initial and final concentrations and the initial and final volumes of circ ulating fluid, due allowance being made for the quantities and volume s removed in sampling. The net absorption rates were expressed as microlitres of water, or as microequivalents or micromoles of solute absorbed per milligram dry weight of intestine per hour (,ul., ,uEq, or

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“…In contrast, it has been pointed out that the regions of the lateral interspaces below the tight junctions are unlikely to represent the locus of discriminatory permeability properties [10], and it seems reasonable to assume that the permeability ratio appropriate to the basal regions of the lateral interspace is unity. It has been shown that the pattern of acid base metabolism in rat jejunum includes secretion of hydrogen ions to the mucosal side and movement of metabolic anions, such as lactate and bicarbonate, into the serosal fluid [16,30]. Since the metabolic anions are not accompanied by hydrogen ions their movements may be expected to increase the pH in the lateral interspace, and it can be seen that this space can be suggested to have permeability properties and a pH value that are qualitatively appropriate to the intermediate compartment of a three-compartment system that performs net transport of weak acids towards the serosal side and of weak bases in the opposite direction.…”

Section: Three-compartment System For Weak Electrolyte Transportmentioning

confidence: 99%

Intestinal Transport of Weak Electrolytes

Jackson

Shiau

Bane

et al. 1974

The Journal of General Physiology

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A study has been made of the transmural fluxes of benzoic, phenylacetic, and pentanoic acids, benzylamine, hexylamine, and D-amphetamine across rat jejunum incubated in vitro. The M to S fluxes of the weak acids were greater than their corresponding S to M fluxes, and the S to M fluxes of the weak bases were larger than their M to S fluxes. These patterns of asymmetric movements were observed when the transmural electrical potential difference was clamped at 0 mV, and when the pH values of the mucosal and serosal fluids were identical. The effects of a weak acid on the fluxes of other weak electrolytes were qualitatively similar when the effector weak acid was added to the mucosal fluid, and when it was added to the serosal fluid. But the effects of a weak base on the fluxes of other weak electrolytes were dependent upon its location, and the interactions observed when the effector weak base was added to the mucosal fluid were qualitatively different than those seen when it was added to the serosal fluid. The interactions between weak electrolytes could readily be explained in terms of the function of a system of three compartments in series, in which the pH of the intermediate compartment is greater than that of the bulk phases. But these observations could not be explained in terms of an analogous system involving an intermediate compartment of low pH, or in terms of a carrier mediated system. The transport function of the three-compartment system can be described in the form of an equation, and it is found that a pH difference of less than 0.5 unit may explain our observations on weak electrolyte transport.The mechanisms involved in the intestinal transport of weak electrolytes have been the subject of several previous investigations. Some studies have demon-

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The Absorption of Bicarbonate‐saline Solutions by the Small Intestine and Colon of the White Rat

Cited by 110 publications

References 4 publications

Transport of sodium and secretion of potassium and bicarbonate by the colon of normal and sodium‐depleted rats

Transport of sodium and secretion of potassium and bicarbonate by the colon of normal and sodium‐depleted rats

The Absorption of Water and Salt From the Small Intestine of the Rat

Intestinal Transport of Weak Electrolytes

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