Role of Aldosterone in the Regulation of Sodium and Chloride Transport in the Distal Colon of Sodium-Depleted Rats

Halevy, Jonathan; Budinger, M. E.; Hayslett, John P.; Binder, Henry J.

doi:10.1016/s0016-5085(86)80021-x

Cited by 71 publications

(62 citation statements)

References 9 publications

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“…This finding appears to confirm the suggestion that the only sodium absorptive process responsive to CO2 is Na/H ion exchange. It also may account for the apparent absence of amiloride-inhibitable Na/H ion exchange in other studies of rat distal colon in which a similar bathing solution sodium concentration of 140 mM was used (19,21,24,25).…”

Section: Discussionmentioning

confidence: 95%

Effects of acid-base variables on ion transport in rat colon.

Goldfarb¹,

Egnor²,

Charney³

1988

J. Clin. Invest.

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Alterations in arterial acid-base variables have important effects on colonic electrolyte transport in vivo. To confirm the relative effects of these variables and to characterize the transport processes involved, we measured unidirectional 22Na and 36C1 fluxes across short-circuited, distal colonic mucosa of Sprague-Dawley rats. Stripped tissues were studied in Hepes buffer and in Ringer's solutions at HCO3 concentrations of 11, 21, and 39 mM, and CO2 tensions between 0 and 69.6 mmHg. Increases in Pco2, but not in either pH or HCO3 concentration, caused similar increases in J.'t and J2, (net flux of sodium and chloride, respectively) from -0.2±03 and -1.5±0.4 ,geq/ cm per h at Pco2 = 0 to 6.8±0.6 and 7.6±0.7 ,ueq/cm2 per h, respectively, at Pco2 = 69.6 mmHg. These increases were accounted for by changes in Jms and were accompanied by small decreases in Isc. 1 mM acetazolamide decreased both J.A= and J~t and their responses to increases in Co2. 0.75 mM luminal amiloride prevented the increase in sodium absorption, but did not affect the C02-induced increase in chloride absorption. In the presence of amiloride, CO2 increased JR (residual flux). 0.1 mM luminal furosemide did not affect the C02-induced increases in J'w in the absence or presence of amiloride.Changes in HCO3 concentration did not alter JRA We conclude that ambient CO2 effects active, electroneutral sodium absorption in the rat distal colon. The process stimulated by CO2 is dependent on mucosal carbonic anhydrase activity and most likely represents Na/H and CI/HCO3 ion exchange.

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Section: Discussionmentioning

confidence: 95%

Effects of acid-base variables on ion transport in rat colon.

Goldfarb¹,

Egnor²,

Charney³

1988

J. Clin. Invest.

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“…The rats were allowed free access to water. One group of rats was fed a sodium-free diet for 7 days, as described previously (16), to produce a secondary increase in serum aldosterone levels (17).…”

Section: Methodsmentioning

confidence: 99%

“…Increased levels of aldosterone as a result of either subcutaneous aldosterone infusion or dietary sodium depletion both induce electrogenic sodium absorption via the epithelial Na ϩ channel ENaC and inhibit electroneutral Na ϩ -Cl Ϫ absorption in rat distal colon as a result of down-regulating both Na ϩ -H ϩ and Cl Ϫ -HCO 3 Ϫ exchanges (15,17). Subsequent studies revealed that aldosterone inhibited the activity, message, and protein of both NHE-2 and NHE-3 isoforms without altering NHE-1 function in colonic epithelial cells (22).…”

Section: Identification Of a Chloride-dependent Namentioning

confidence: 99%

Cloning and Expression of a Chloride-dependent Na+-H+ Exchanger

Sangan¹,

Rajendran²,

Geibel³

et al. 2002

Journal of Biological Chemistry

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Electroneutral Na؉ -H ؉ exchange is present in virtually all cells, mediating the exchange of extracellular Na ؉ for intracellular H ؉ and, thus, plays an important role in the regulation of intracellular pH, cell volume, and transepithelial Na ؉ absorption. Recent transport studies demonstrated the presence of a novel chloridedependent Na ؉ -H ؉ exchange in the apical membrane of crypt cells of rat distal colon. We describe the cloning of a 2.5-kb full-length cDNA from rat distal colon that encodes 438 amino acids and has six putative transmembrane spanning domains. Of the 438 amino acids 375 amino acids at the N-terminal region are identical to Na ؉ -H ؉ exchange (NHE)-1 isoform with the remaining 63 amino acids comprising a completely novel C terminus. In situ hybridization revealed that this transcript is expressed in colonic crypt cells, whereas Northern blot analysis established the presence of its 2.5-kb mRNA in multiple tissues. Despite its much smaller size compared with all other known Na ؉ -H ؉ exchange isoforms, NHEdeficient PS120 fibroblasts stably transfected with this cDNA exhibited Na ؉ -dependent intracellular pH recovery to an acid load that was chloride-dependent and inhibited both by 5-ethylisopropylamiloride, an amiloride analogue, and by 5-nitro-2-(3-phenylproplyamino)-benzoic acid, a Cl ؊ channel blocker, but only minimally affected by 25 M 3-methylsulfonyl-4piperidonbenzoyl-guanidine, an NHE-1 and NHE-2 isoform inhibitor.

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“…The principal effect of aldosterone, which is clearly established at 24 h and becomes more marked thereafter, is to enhance amiloride-sensitive electrogenic Na+ transport (Halevy et al 1986). Stimulation of rat distal colon by aldosterone for 3-7 days or longer further enhances amiloride-sensitive electrogenic Na+ transport and completely inhibits amiloride-insensitive electroneutral NaCl absorption (Foster et al 1983;Halevy et al 1986).…”

Section: Implications For Na+ Transportmentioning

confidence: 99%

Effects of corticosteroid hormones on the electrophysiology of rat distal colon: implications for Na+ and K+ transport.

Binder

McGlone

Sandle

1989

The Journal of Physiology

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SUMMARY1. Conventional microelectrodes, the Na+ channel blocker amiloride (0-1 mM), and the K+ channel blocker tetraethylammonium chloride (TEA, 30 mM) were used to examine the effects of corticosteroid hormones administered in vivo on the Na+ and K+ transport properties of isolated rat distal colon. The cell membrane changes induced by aldosterone (a specific mineralocorticoid), RU 28362 (a synthetic glucocorticoid with negligible affinity for mineralocorticoid receptors), and dexamethasone (an activator of both mineralocorticoid and glucocorticoid receptors) were compared.2. In control animals, there was no amiloride-sensitive apical Na+ conductance, and only a relatively small TEA-sensitive apical K+ conductance.3. Hyperaldosteronism secondary to dietary Na+ depletion for 10-14 days, dexamethasone (600 jug 100 g-' day-' for 3 days), and RU 28362 (600 ,ug 100 g-1 day-' for 3 days) induced amiloride-sensitive electrogenic Na+ transport, with the potency of aldosterone > dexamethasone > RU 28362.4. With each corticosteroid, increased electrogenic Na+ transport reflected enhanced apical Na+ conductance, and in the case of aldosterone and dexamethasone, 3 3-fold and 2-fold increases respectively in the maximum activity of the basolateral Na+-K+ pump. In contrast, RU 28362 suppressed the maximum activity of the basolateral Na+-K+ pump by 45 %.5. All three corticosteroids enhanced the K+ conductance of the apical membrane, with the potency of aldosterone > dexamethasone > RU 28362.6. Co-administration of spironolactone (5 mg 100 g-' day-') inhibited the effects of aldosterone on Na+ and K+ transport, but in dexamethasone-treated animals spironolactone resulted in a pattern of response similar to that found in RU 28362-treated animals.7. The results support the view that mineralocorticoid receptors mediate changes in colonic Na+ and K+ transport which differ quantitatively and qualitatively from those mediated by glucocorticoid receptors. Dexamethasone and similar 'glucocorticoids' activate both types of receptor, with an overall epithelial response which mimics that induced by aldosterone.t To whom reprint requests should be sent.

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Role of Aldosterone in the Regulation of Sodium and Chloride Transport in the Distal Colon of Sodium-Depleted Rats

Cited by 71 publications

References 9 publications

Effects of acid-base variables on ion transport in rat colon.

Effects of acid-base variables on ion transport in rat colon.

Cloning and Expression of a Chloride-dependent Na+-H+ Exchanger

Effects of corticosteroid hormones on the electrophysiology of rat distal colon: implications for Na+ and K+ transport.

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