Electrogenic sodium absorption in rabbit cecum in vitro.

Sellin, Joseph H.; Oyarzabal, Hector; Cragoe, E J

doi:10.1172/jci113445

Cited by 24 publications

(13 citation statements)

References 32 publications

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“…Halevy et al (25) reported that RU 28362 infused into rats for 24 h increased amiloride-insensitive Isc which may represent either active chloride secretion or amiloride-resistant, electrogenic sodium transport. The former has been shown to be stimulated by dexamethasone and methylprednisolone in rat distal colon (26) and rat ileum (27), respectively, and the latter was recently described in the rabbit cecum (28). Unfortunately, neither ion flux measurements nor ion replacement studies were performed to establish the basis for this increase in Isc.…”

Section: Discussionmentioning

confidence: 99%

Regulation of active sodium and potassium transport in the distal colon of the rat. Role of the aldosterone and glucocorticoid receptors.

Turnamian¹,

Binder²

1989

J. Clin. Invest.

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To determine whether mineralocorticosteroids and glucocorticosteroids have specific effects on colonic electrolyte transport, we compared the effect of aldosterone and RU 28362, a glucocorticoid receptor-specific agonist that does not bind to the aldosterone receptor, on unidirectional Na, Cl, and K fluxes across isolated mucosa of the rat distal colon. Continuous infusion of aldosterone for 7 d produced changes in four specific transport processes: induction of both active electrogenic, amiloride-sensitive sodium absorption and active electrogenic potassium secretion, enhancement of active electroneutral potassium absorption, and inhibition of electroneutral Na-Cl absorption, the predominant transport process in this epithelium. In contrast, continuous infusion of RU 28362 for 1-11 d produced a sustained increase in electroneutral Na-Cl absorption. This glucocorticoid receptor-specific agonist did not induce electrogenic sodium absorption nor affect either potassium absorption or secretion. These studies demonstrate that aldosterone (i.e., mineralocorticoid) and glucocorticoid receptors modulate separate and specific changes in active sodium and potassium transport. These results suggest that other glucocorticoids (e.g., dexamethasone, methylprednisolone) are not glucocorticoid receptor-specific and that their effects on electrogenic sodium absorption and potassium transport most likely represent the binding of these agonists to the aldosterone receptor.

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Section: Discussionmentioning

confidence: 99%

Regulation of active sodium and potassium transport in the distal colon of the rat. Role of the aldosterone and glucocorticoid receptors.

Turnamian¹,

Binder²

1989

J. Clin. Invest.

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“…However, in contrast to the guinea-pig distal colon, in the caecum the electrogenic part of Na+ absorption appears to be relatively insensitive to amiloride inhibition (Rechkemmer, 1988). Amiloride-insensitive electrogenic Na+ transport has recently been demonstrated for the rabbit caecum (Sellin, Oyarzabal & Cragoe, 1988). In contrast to the rabbit caecum, however, in the guinea-pig caecum incubation with a Na+-free solution led to a drastic increase in tissue conductance.…”

Section: Na+-h+ Exchange and Scfa Transportmentioning

confidence: 98%

Effects of amiloride and ouabain on short‐chain fatty acid transport in guinea‐pig large intestine.

Engelhardt

Burmester

Hansen

et al. 1993

The Journal of Physiology

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SUMMARY1. Effects of H+ secreting mechanisms on unidirectional passage of the short-chain fatty acids (SCFA) acetate, propionate and n-butyrate across isolated guinea-pig caecum, proximal and distal colon were studied under short-circuit current conditions in Ussing chamber isotope flux experiments.2. In the caecum and the proximal colon the serosal-to-mucosal fluxes (Jsm) were higher than the mucosal-to-serosal fluxes (Jms). Thus a net secretion of SCFA was present in the caecum and proximal colon. The higher Jrm appears to be coupled to the Na+ gradient established by the basolateral membrane Na+-K+-ATPase, whereas Jms is related to the operation of an apical membrane Na+-H+ exchanger. Inhibition of Na+-H+ exchange by amiloride (1 mM) added to the mucosal solution decreased Jms of SCFA in caecum and in proximal colon, but had no major effect in distal colon.3. In distal colon Jms exceeds Jsm and thus a net absorption of SCFA was observed.Jms is Na+ independent and coupled to the activity of the apical membrane K+-H+-ATPase. Inhibition of the K+-H+-ATPase by addition of ouabain (0-1 mM) to the mucosal solution diminished Jms in the distal colon; in the caecum and proximal colon ouabain had no effect on Jms.4. Neither amiloride nor ouabain caused major changes in J. in any of the large intestinal segments.5. In conclusion, absorption of SCFA, e.g. Jms, in all large intestinal segments is related to the presence and activity of H+ secreting systems located in the apical membrane of colonocytes. In the caecum and proximal colon the predominant system appears to be Na+-H+ exchange, and in the distal colon K+-H+-ATPase. Supply of H+ ions allows protonation of SCFA anions and subsequent permeation by non-ionic diffusion across the apical membrane. These mechanisms account for 35, 40-50 and 60-80% of SCFA transport in the caecum, the proximal and the distal colon of guinea-pig, respectively.

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“…In addition, surgical masks and disposable gloves were used. In the proximal colon of rats, sodium is transported across the apical membrane by an electroneutral Na + /H + exchange (Binder et al, 1986;Foster et al, 1986a, b (Sellin et al, 1988). !!…”

Section: Animals and Preparationsmentioning

confidence: 99%

Sodium transport across the caecal and colonic epithelium of germfree and specific-pathogen free rats

Rösel¹,

Engelhardt²

1996

Reprod. Nutr. Dev.

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Summary ― It was assumed that the enlarged caecum and the accumulation of semiliquid contents in germfree rats is accompanied by changes in sodium absorption. Transepithelial sodium fluxes were studied under Ussing chamber conditions across epithelial sheets of the caecum and colon of germfree (GF) and specific-pathogen free (SPF) rats. Net sodium transport was highest in the proximal colon and in the proximal segment of the distal colon; it was considerably lower in the caecum and in the distal segment of the distal colon. In the caecum and proximal colon of the GF rats, the electroneutral sodium absorption was increased as compared to the SPF rats. In the proximal segments of the distal colon, no differences were seen. In the distal segment of the distal colon, the mainly electroneutral sodium transport in the SPF rats was changed into electrogenic transport in the GF rats. These differences may be due to the increased aldosterone levels of the GF rats.germfree / specific-pathogen free / rat / caecum / colon / sodium transport / in vitro Résumé -Transport du sodium à travers l'épithélium caecal et colique chez des rats axéniques ou sans germes pathogènes. L'hypothèse initiale du présent travail était que des modifications de l'absorption du sodium accompagnent l'élargissement du caecum et l'accumulation de contenus semiliquides chez des rats axéniques. Les flux transépithéliaux de sodium ont été étudiés, dans les conditions de chambre d'Ussing, à travers des parois épithéliales de caecum et de côlon de rats axéniques (GF) ou sans germes pathogènes (SPF). Le transport net du sodium était le plus élevé dans le côlon proximal et dans le segment proximal du côlon distal ; il était considérablement plus faible dans le caecum et dans le segment distal du côlon distal. L'absorption électroneutre du sodium dans le caecum et le côlon proximal était augmentée chez les rats GF par rapport aux rats SFP. Aucune différence n'a été observée dans les segments proximaux du côlon distal. Dans le segment distal du côlon distal, le transport du sodium, surtout électroneutre chez les rats SFP, devenait électrogénique chez les rats GF. Ces différences pourraient être dues aux niveaux accrus d'aldostérone chez les rats GF.

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Electrogenic sodium absorption in rabbit cecum in vitro.

Cited by 24 publications

References 32 publications

Regulation of active sodium and potassium transport in the distal colon of the rat. Role of the aldosterone and glucocorticoid receptors.

Regulation of active sodium and potassium transport in the distal colon of the rat. Role of the aldosterone and glucocorticoid receptors.

Effects of amiloride and ouabain on short‐chain fatty acid transport in guinea‐pig large intestine.

Sodium transport across the caecal and colonic epithelium of germfree and specific-pathogen free rats

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