Epithelial transport pathways of rat colon determined in vivo by impulse response analysis.

Edmonds, C. J.; Smith, Thomas P.

doi:10.1113/jphysiol.1979.sp013017

Cited by 17 publications

(16 citation statements)

References 15 publications

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“…To see how active Na absorption was affected, the flux ratio equation (Ussing, 1952) was used to estimate the passive component of the flux, JP5. Previous studies (Edmonds & Smith, 1979) (Table 2). In the adrenalectomized rats, active Na absorption, like the p.d., was unaffected by amiloride.…”

Section: Influence Of Luminal Na Concentration and Kmentioning

confidence: 92%

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Amiloride sensitivity of the transepithelial electrical potential and of sodium and potassium transport in rat distal colon in vivo.

Edmonds¹

1981

The Journal of Physiology

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Section: Influence Of Luminal Na Concentration and Kmentioning

confidence: 92%

“…Recently presented evidence (Edmonds & Smith, 1979) indicated that K, unlike Na, Cl and various other ions, crosses the epithelium not only by the paracellular pathway but largely by a K-selective pathway (Fig. 5).…”

Section: Plasma-to-lumen K Fluxmentioning

confidence: 99%

Amiloride sensitivity of the transepithelial electrical potential and of sodium and potassium transport in rat distal colon in vivo.

Edmonds¹

1981

The Journal of Physiology

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“…The mucosa-to-serosa flux of inulin was even reported to be higher in the colon than in the small intestine [19]. Furthermore, urea is transported from the plasma into the lumen in rats, sheep and goats, and in a concentration-dependent way in the latter two animals [4,5]. Thus, the results are conflicting and some of the results are difficult to reconcile with the description of the colonic epithelium as being fairly tight.…”

Section: Introductionmentioning

confidence: 99%

Permeability of the proximal and distal rat colon crypt and surface epithelium to hydrophilic molecules

Fihn

Jodal

2000

Pflügers Arch - Eur J Physiol

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Our knowledge of the epithelial permeability of different sections of the colon as well as of the surface and crypt epithelium is patchy and contradictory. Therefore, movement of radiolabelled urea, mannitol and Cr-EDTA between the lumen and the plasma of rats was studied, and expressed as clearance. In experiments studying movement from the lumen to the plasma, only the clearance of urea was significant. In experiments on the movement from plasma to the lumen, all three permeability probes exhibited significant clearance in the proximal colon, while in the distal colon the clearance of Cr-EDTA was not significant and the other clearance values were lower than in the proximal colon. Thus, the two methods are proposed to mainly reflect the permeability of two different parts of the epithelium, i.e. the surface and the crypt epithelium. Furthermore, it is proposed that the rat surface epithelium only allows passage of hydrophilic substances smaller than monosaccharides [radius below 0.35 nm (3.5 A] while the crypt epithelium, particularly in the proximal colon, is a heteroporous membrane of higher permeability containing pores corresponding to radii of >3.5-4.0 nm (35-40 A) and 0.4-0.5 nm (4-5 A). Moreover, the results indicate that in vivo luminal fluid solution has no access to the crypt epithelium, a conclusion strengthened by the observation that Evans-blue-labelled albumin and FITC-dextran 4000 do not seem to reach the crypt lumina.

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“…Moreover, it seems likely that the secreted potassium is largely derived from the abundant potassium contained in the epithelial cells (Wills & Biagi, 1982). Previous kinetic studies indicated that the secreted potassium came from a potassium pool with a relatively fast turnover, a finding consistent with the existence of an epithelial cell secreting mechanism (Edmonds & Smith, 1979). Using 86 Rb+ as an analogue of potassium we have, therefore, in the present work also examined the origin of the secreted potassium, particularly in relation to the variable rates of potassium secretion.…”

Section: Introductionmentioning

confidence: 76%

“…Ordinarily in the distal colon, chloride appears to move from plasma to lumen by way of the paracellular route (Edmonds & Smith, 1979) and an increase of chloride permeability of the paracellular pathway could account for the observed rise of chloride secretion. That sodium movement into the colonic lumen was also increased in the rats on the normal diet lends some support to the possibility that the paracellular pathway had become more 'leaky ' during the infusion, to both sodium and chloride.…”

Section: Discussionmentioning

confidence: 99%

The effect of dietary sodium and potassium intake on potassium secretion and kinetics in rat distal colon.

Edmonds¹,

Willis²

1990

The Journal of Physiology

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SUMMARY1. Potassium secretion by the distal colon was examined in relation to the secretion of chloride and absorption of sodium and to the epithelial turnover of 86Rb+ (as an analogue of potassium) in vivo in rats fed a standard, a potassium-rich or a sodium-depleted diet.2. An acute intravenous potassium load stimulated potassium secretion two-to threefold. In rats fed the standard diet, sodium secretion was also increased but no significant change in the lumen-to-plasma sodium flux was detected. The potassium and sodium secretions were accompanied by increased chloride secretion which occurred even when the intravenous load contained no chloride. In rats fed the potassium-rich diet, there was a small increase in sodium absorption and a less marked increase of chloride secretion. In the sodium-depleted rats, however, about 70-80% of the increased potassium secretion was balanced by increased sodium absorption.3. The epithelial turnover rate of 86Rb+ in the rats fed the potassium-rich (t1 12-14 min) and the sodium-depleted (tj 11-13 min) diets was faster than that of those of the standard diet (t1 22-27 min). 4. The epithelial potassium content was 304 + 9 nmol (mg dry weight)-' and was not significantly altered despite considerable variations in potassium secretion rate induced by dietary changes and acute potassium loading.5. It is concluded that epithelial potassium turnover rate is increased during chronic states of increased potassium secretion and that the rise in potassium secretion is consistent with increased activity of the basolateral Na+-K+ pump. Whether the increased potassium secretion is associated with chloride secretion or with increased sodium absorption appears to depend on the absence or presence of the amiloride-sensitive sodium pathway in the apical membrane.

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Epithelial transport pathways of rat colon determined in vivo by impulse response analysis.

Cited by 17 publications

References 15 publications

Amiloride sensitivity of the transepithelial electrical potential and of sodium and potassium transport in rat distal colon in vivo.

Amiloride sensitivity of the transepithelial electrical potential and of sodium and potassium transport in rat distal colon in vivo.

Permeability of the proximal and distal rat colon crypt and surface epithelium to hydrophilic molecules

The effect of dietary sodium and potassium intake on potassium secretion and kinetics in rat distal colon.

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