Basic–Alimentary TractAn alternate pathway of cAMP-stimulated Cl− secretion across the NKCC1-null murine duodenum☆,☆☆
Section snippets
Animals
Mice with gene-targeted disruption (knockout) of NKCC1 (locus Slc12a2) were developed as previously described.9 At 3–6 weeks of age, offspring were genotyped using primers specific for murine NKCC1 and the disrupted allele. Age-matched NKCC1 (+/+) and NKCC1 (−/−) siblings 2–5 months of age were used for experimentation. The mice were fed a standard laboratory chow (Formulab 5008 Rodent Chow; Ralston Purina, St. Louis, MO) and water ad libitum. Before each experiment, the mice were fasted
pH stat studies
The JsmHCO3 and Isc were measured over 3 consecutive 30-minute periods (basal, forskolin, and forskolin + bumetanide) in NKCC1+/+ and NKCC1−/− duodena. The normalized Isc was converted to μeq/cm2 · h for comparison with the JsmHCO3. In NKCC1+/+ duodenum (Figure 1A), both Isc and JsmHCO3 showed stable rates throughout the basal period (period 1).
Discussion
The anion secretory response to stimulation of intracellular cyclic nucleotides in intestinal epithelia involves the combined efflux of Cl− and HCO3− ions across the apical membrane by electrogenic processes requiring the anion channel function of CFTR.4 As predicted from the model developed by Field and others,28 completion of the current pathway for sustained Cl− secretion necessitates a process of Cl− uptake across the basolateral membrane of epithelial cells. Molecular cloning, biochemical,
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Molecular mechanisms underlying guanylin-induced transcellular Cl<sup>−</sup> secretion into the intestinal lumen of seawater-acclimated eels
2022, General and Comparative EndocrinologyCitation Excerpt :In the eel intestine, ca2b was abundantly expressed and upregulated after SW acclimation (Takei, 2021). In the Slc12a2−/− mice, Cl− uptake occurs via coupled AE2 and NBCel in the duodenum (Walker et al., 2002). Thus, Cl− uptake by coupling of these transporters may be common in vertebrate intestines.
Novel Human NKCC1 Mutations Cause Defects in Goblet Cell Mucus Secretion and Chronic Inflammation
2020, Cellular and Molecular Gastroenterology and HepatologyCitation Excerpt :Thus, it seems that the signaling pathways that control goblet cell differentiation in the intestine are normal in both NKCC1-DFX and NKCC1 KO mice, making it unlikely that the mucus thinning is caused by a deficit in goblet cell number. Because of the role of NKCC1 in Cl- and HCO3- secretion,31 it is far more likely that the thinner mucus layer is caused by impaired mucus expansion. Indeed, in airway epithelial cells bathed in a HCO3--free saline, it was shown that application of bumetanide led to the production of strands of mucus that were abnormally viscous.32
Molecular Basis and Differentiation-Associated Alterations of Anion Secretion in Human Duodenal Enteroid Monolayers
2018, Cellular and Molecular Gastroenterology and HepatologyCitation Excerpt :Specifically, 75% of the forskolin-induced ΔIsc was inhibited by bumetanide in undifferentiated enteroids and 44% in differentiated enteroids. This is consistent with the in vivo observation that bumetanide inhibited a large part of forskolin-induced ΔIsc without affecting bicarbonate secretion in mouse duodenum.33 Fourth, a bumetanide-insensitive component of forskolin-induced ΔIsc was observed in both undifferentiated and differentiated enteroids.
Ae4 (Slc4a9) anion exchanger drives Cl<sup>-</sup> uptake-dependent fluid secretion by mouse submandibular gland acinar cells
2015, Journal of Biological ChemistryCitation Excerpt :Indeed, disruption of Nkcc1 expression in mouse parotid glands confirmed that a considerable residual saliva secretion remains in the absence of Na+-K+-2Cl− cotransporter activity. It has been proposed that this secondary Cl− uptake pathway depends on Cl−/HCO3− exchanger activity in secretory epithelial cells (39, 42–46). Although the molecular identity of the anion exchanger in salivary gland acinar cells is unknown, this HCO3−-dependent mechanism appears to play an important role for Cl− uptake during prolonged muscarinic stimulation (9, 11, 14, 47).
Gastroduodenal Bicarbonate Secretion
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2012, Physiology of the Gastrointestinal Tract
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Address requests for reprints to: Lane L. Clarke, D.V.M., Ph.D., 324D Dalton Cardiovascular Research Center, Research Park Drive, University of Missouri-Columbia, Columbia, Missouri 65211. e-mail: [email protected]; fax: (573) 884-4232.
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Supported by grants RO1 DK48816 and RO1 DK50594 from the National Institutes of Health.