Cell Na+ activities and transcellular Na+ absorption by descending colon from normal and Na+-deprived rabbits

Turnheim, Klaus; Hudson, Randall L.; Schultz, Stanley G.

doi:10.1007/bf00580277

Cited by 20 publications

(4 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There is abundant experimental evidence that adrenal corticosteroids increase and adrenalectomy decreases Na + transport and the permeability of the apical membrane of colonocytes to Na § [2,3,6,29,41]. The corticosteroids increase Na § flux into the cell which in turn stimulates the active Na + extrusion via the Na,K pump, because the intracellular Na + activity remains approximately constant in spite of the manifold variations of Na + current across the epithelium [38]. There are, in addition, indications that the Na,K pump itself may be influenced directly by corticosteroids.…”

Section: Introductionmentioning

confidence: 98%

Na, K-ATPase and the development of Na+ transport in rat distal colon

et al. 1991

View full text Add to dashboard Cite

Na,K-ATPase function was studied in order to evaluate the mechanism of increased colonic Na+ transport during early postnatal development. The maximum Na(+)-pumping activity that was represented by the equivalent short-circuit current after addition of nystatin (ISCN) did not change during postnatal life or after adrenalectomy performed in 16-day-old rats. ISCN was entirely inhibited by ouabain; the inhibitory constant was 0.1 mM in 10-day-old (young) and 0.4 mM in 90-day-old (adult) rats. The affinity of the Na,K pump for Na+ was higher in young (11 mM) than in adult animals (19 mM). The Na,K-ATPase activity (measured after unmasking of latent activity by treatment with sodium dodecylsulfate) increased during development and was also not influenced by adrenalectomy of 16-day-old rats. The inhibitory constant for ouabain (KI) was not changed during development (0.1-0.3 mM). Specific [3H]ouabain binding to isolated colonocytes increased during development (19 and 82 pmol/mg protein), the dissociation constant (KD) was 8 and 21 microM in young and adult rats, respectively. The Na+ turnover rate per single Na,K pump, which was calculated from ISCN and estimated density of binding sites per cm2 of tissue was 500 in adult and 6400 Na+/min.site in young rats. These data indicate that they very high Na+ transport during early postnatal life reflects an elevated turnover rate and increased affinity for Na+ of a single isoform of the Na,K pump. The development of Na+ extrusion across the basolateral membrane is not directly regulated by corticosteroids.

show abstract

Section: Introductionmentioning

confidence: 98%

Na, K-ATPase and the development of Na+ transport in rat distal colon

et al. 1991

View full text Add to dashboard Cite

show abstract

“…In the latter, Na + absorption across the epithelium is a two‐step, electrogenic process involving mucosal amiloride‐sensitive Na + channels and active transport across the basolateral membrane via the Na + ‐K + ‐ATPase (McCabe et al 1982). The rate‐limiting step in this process is apical amiloride‐sensitive Na + entry (Thompson & Sellin, 1986; Turnheim et al 1987). The epithelial Na + channel (ENaC) complex is composed of three homologous subunits, α, β and γ (McDonald et al 1994; Prince & Welsh, 1998; Stokes & Sigmund, 1998).…”

mentioning

confidence: 99%

Effects of butyrate on active sodium and chloride transport in rat and rabbit distal colon

Vidyasagar

Ramakrishna

2002

The Journal of Physiology

View full text Add to dashboard Cite

Short chain fatty acids, particularly butyrate, stimulate electroneutral NaCl absorption from the colon. Their effect in colonic epithelia lacking basal electroneutral NaCl absorption is unknown. Butyrate is also reported to inhibit active Cl− secretion in the colon. The present studies were undertaken to investigate the inter‐relationships between the effects of butyrate on active Na+ and Cl− transport in the colon. Studies were carried out in rabbit distal colon (known to have predominant electrogenic Na+ absorption), rat distal colon (characterised by electroneutral Na+ absorption), and hyperaldosteronaemic rat distal colon (characterised by electrogenic Na+ absorption). The effect of cholera toxin (CT) was also noted. Potential difference, short‐circuit current (ISC) and fluxes of Na+ and Cl− were measured in stripped mucosa under voltage‐clamp conditions. Butyrate stimulated electroneutral Na+ and Cl− absorption in distal colon of normal and salt‐depleted rats, and stimulated Na+ absorption in rabbit distal colon. Amiloride (10−4m) or CT did not inhibit this process. In rabbit distal colon, stimulation of Na+ absorption by butyrate was not dependent on the presence of Cl− in the medium. Butyrate significantly decreased conductance, decreased flux of sodium from serosa to mucosa (particularly in rabbit distal colon), and decreased ISC. Net Cl− secretion, induced by CT, was completely inhibited by butyrate. Stimulation of Na+ absorption was independent of exposure to CT. Bumetanide reversed net Cl− secretion to net absorption, but did not alter Na+ or Cl− fluxes in tissues exposed to butyrate. Thus butyrate stimulates active Na+ absorption in colonic epithelia, with or without expression of basal Na+‐H+ exchange. Independently, butyrate inhibits active Cl− secretion induced by cAMP in these epithelia.

show abstract

Section: Reconciliation Of the New Model For Fluid Absorption Withmentioning

confidence: 99%

“…Under normal circumstances, the rate of Na + extrusion into the basolateral space is linked directly to intracellular Na + concentration and therefore, indirectly to Na + entry (Turnheim et al 1987). The low intracellular concentration of Na + provides the concentration gradient for Na + entry across the brush border membrane.…”

Section: Experimentally-based Evidencementioning

confidence: 99%

A reconsideration of the evidence forEscherichia coliSTa (heat stable) enterotoxin-driven fluid secretion: a new view of STa action and a new paradigm for fluid absorption

Lucas

2001

Journal of Applied Microbiology

View full text Add to dashboard Cite

A review of the evidence for Escherichia coli STa causinḡ uid secretion in vivo leads to the conclusion that the concept of STa acting through enhanced chloride secretion in order to derange intestinal function is unproven. However, a consistent effect of STa in the small intestine is on Na + /H + exchange, leading to interruption of luminal acidi®cation. A model for the action of STa, involving inhibition of Na + /H + exchange, is proposed which explains the ability of STa to reduce absorption in vivo but its inability to cause secretion in vivo in contrast to its apparent secretory effect in vitro. The apparent ability to demonstrate secretion in vitro is shown to derive from methodologies which do not involve measurement of mass transport of water but instead, infer it from in vitro and in vivo proxy measurements. The in vitro demonstration of notional secretion after STa exposure can be reconciled with the proposed new model for¯uid absorption in that cell swelling is argued to arise as a transient consequence of STa challenge followed by regulatory volume decrease. Evidence for this derangement model is presented in the form of observations derived from acute in vivo physiological studies and clinical studies on patients without the exchanger. This process of appraisal of the evidence for the mechanism of action of STa has led to a new model for¯uid absorption. This is based on the formation of hypotonicity at the brush border luminal surface rather than hypertonicity within the lateral spaces as required by the present standing gradient model of¯uid absorption. Evidence from the literature is presented for this new paradigm of water absorption, which may only be relevant for small intestine and other tissues that have Na + /H + exchangers in contact with HCO 3 ) -containing solutions but which may also be generalizable to all mammalian absorbing epithelial membranes.

show abstract

Cell Na+ activities and transcellular Na+ absorption by descending colon from normal and Na+-deprived rabbits

Cited by 20 publications

References 29 publications

Na, K-ATPase and the development of Na+ transport in rat distal colon

Na, K-ATPase and the development of Na+ transport in rat distal colon

Effects of butyrate on active sodium and chloride transport in rat and rabbit distal colon

A reconsideration of the evidence forEscherichia coliSTa (heat stable) enterotoxin-driven fluid secretion: a new view of STa action and a new paradigm for fluid absorption

Contact Info

Product

Resources

About