Calcium dependence of basal electrolyte transport in rabbit ileum

Donowitz, Mark; Asarkof, N.

doi:10.1152/ajpgi.1982.243.1.g28

Cited by 35 publications

(17 citation statements)

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“…The methods used to measure active ileal electrolyte transport have been described previously (4). In brief, stripped ileal mucosa was mounted as a flat sheet between two lucite modified Ussing chambers that had an area of 1.13 cm2, oxygenated, and maintained at 37°C.…”

Section: Methodsmentioning

confidence: 99%

Elevated intracellular Ca2+ acts through protein kinase C to regulate rabbit ileal NaCl absorption. Evidence for sequential control by Ca2+/calmodulin and protein kinase C.

et al. 1989

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Calcium/calmodulin is involved in the regulation of basal rabbit ileal active Na and CI absorption, but the mechanism by which elevated intracellular Ca2" affects Na and Cl transport is unknown. To investigate the roles of the Ca2+/calmodulin and protein kinase C systems in ileal NaCl transport, two drugs, the isoquinolenesulfonamide, H-7, and the naphthalenesulfonamide, W13, were used in concentrations that conferred specificity in the antagonism of protein kinase C (60 MM H-7) and Ca2+/calmodulin (45 MM W13), respectively, as determined using phosphorylation assays in ileal villus cells. W13 but not H-7 stimulated basal active NaCl absorption. H-7 inhibited changes in Na and Cl absorption caused by maximal concentrations of Ca2" ionophore A23187 and carbachol and serotonin, secretagogues that act by increasing cytosol Ca2", while W13 had no effect. In contrast, neither H-7 nor W13 altered the change in NaCl transport caused by the cyclic nucleotides 8-Br-cAMP and 8-Br-cGMP. These data suggest that: (a) basal rabbit ileal NaCl absorption is regulated by the Ca2'/ calmodulin complex and not by protein kinase C; (b) the effect of elevating intracellular Ca2" to decrease NaCI absorption is mediated via protein kinase C but not by Ca2+/calmodulin; (c) the effects of protein kinase C are not overlapping or synergistic with those of Ca2+/calmodulin on either basal absorption or on the effects of increased Ca2+; and (d) neither Ca2+/calmodulin nor protein kinase C are involved in the effects of cAMP and cGMP on ileal active NaCl transport.

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Section: Methodsmentioning

confidence: 99%

Elevated intracellular Ca2+ acts through protein kinase C to regulate rabbit ileal NaCl absorption. Evidence for sequential control by Ca2+/calmodulin and protein kinase C.

et al. 1989

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“…However, while dopamine also increased the se- This pattern of change in electrolyte transport caused by dopamine is similar to changes in active Na and Cl absorption previously described in rabbit ileum with exposure to other neurohumoral substances including epinephrine, norepinephrine, somatostatin, and the enkephalins (1,2,16,23,24); and to the drugs aspirin and chloroquine applied to the ileal serosal surface (5,17). It is also similar to the pattern of change brought about by exposure of ileum to calcium-free bathing solutions on mucosal plus serosal surfaces or to verapamil, a "calcium channel" blocker, which presumably lowers cell calcium (18). Where studied, this stimulation of Na and Cl absorption was associated with an increase in Na and Cl influx across the brush border and most probably occurs via the so-called neutral NaCl absorptive process (26).…”

Section: Discussionmentioning

confidence: 55%

“…In addition, a change in total ileal calcium content, which represents primarily intracellular calcium stores, is only an indirect reflection of a change in cytosolicfree calcium, which is thought to be the effective calcium pool (31). However, lowering of intracellular calcium and stimulation of Na and Cl absorption, as caused by exposure to dopamine, are the same changes in total ileal calcium and ion transport caused by ileal exposure to 1-verapamil, a calcium channel blocker, and to calcium-free bathing solutions (18). In addition, the decrease in total ileal calcium content caused by dopamine could have been caused either by a decrease in influx of Ca++ or an increase in efflux.…”

Section: Discussionmentioning

confidence: 99%

Dopamine Stimulation of Active Na and Cl Absorption in Rabbit Ileum

Donowitz¹,

Cusolito²,

Battisti³

et al. 1982

J. Clin. Invest.

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A B S T R A C T The effects of dopamine on active intestinal ion transport have been evaluated. An epithelial sheet preparation of rabbit ileum was used in vitro with the Ussing chamber-voltage clamp technique. Dopamine, in the presence of 1 mM ascorbic acid, added to the serosal bathing solution caused a dosedependent decrease in short-circuit current, with a half-maximal effect at 1.2 MM and maximal effect of -50 uA/cm2 at 50 ,M; dopamine decreased the potential difference, and increased the conductance and net Na and net Cl absorption. There was no effect on the residual ion flux. Dopamine did not alter the change in short-circuit current caused by mucosal glucose (10 mM) or serosal theophylline (10 mM). Mucosal dopamine had no effect. The effect of dopamine on short-circuit current was inhibited by the dopamine antagonists haloperidol and domperidone and the a2-adrenergic antagonist yohimbine; there was no effect of the a,-antagonist prazosin and the ,3-antagonist propranolol. In addition, the a2-adrenergic agonist clonidine, but not the cal-agonist methoxamine caused a dose-dependent decrease in short-circuit current. The ileal effects of dopamine did not occur via conversion into norepinephrine or release of norepinephrine from the peripheral nerves since "peripheral sympathectomy" with 6-hydroxydopamine did not alter the dopamine-induced change in ileal short-circuit current. The dopamine effects were not associated with a change in basal ileal cyclic AMP content but were associated with a decrease in total ileal calcium content as measured by atomic absorption spectrometry and as estimated by 45Ca++ uptake. The decrease in calcium content could be attributed to a dopamine-induced decrease in 45Ca++ influx from the serosal surface. Because of the presence of dopamine in ileal mucosa and these effects on ileal electrolyte transport, it is possible that dopamine may be involved in the physiologic regulation of active intestinal electrolyte absorption.

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“…Alterations in serosal solution Ca2' concentration change Na+ and Cl-fluxes in a fashion that cannot be ascribed to modifications of epithelial passive permeability (1)(2)(3)(4). Calcium deprivation increases Na+ and Cl-absorption, whereas high Ca2' concentrations inhibit Na+ and Cl-absorption, cause Cl-secretion, or both.…”

mentioning

confidence: 99%

“…Calcium deprivation increases Na+ and Cl-absorption, whereas high Ca2' concentrations inhibit Na+ and Cl-absorption, cause Cl-secretion, or both. The effect of Ca2" deprivation is reproduced by the Ca2"-channel blocker verapamil (1). Furthermore, NaCl absorption is inhibited or Cl-secretion is stimulated by the Ca2" ionophore A23187 (3,4), by serotonin (5), and by carbamoylcholine (3) only if Ca2+ is present in the serosal solution.…”

mentioning

confidence: 99%

Calcium/calmodulin inhibition of coupled NaCl transport in membrane vesicles from rabbit ileal brush border.

Fan¹,

Powell²

1983

Proc. Natl. Acad. Sci. U.S.A.

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The role of Ca2" and calmodulin in regulating coupled NaCl transport has been investigated in membrane vesicles from rabbit ileal brush border. Uptake of 'Na' and 'Clwas determined by a rapid filtration technique in vesicles isolated with a sucrose density gradient ultracentrifugation method. Ca2+ on the inside of the vesicle inhibited Na' uptake when ClP was the anion and Cl-uptake when Na+ was the cation by =30%. Ca2+ on the outside had no effect. When gluconate was the anion or when choline was the cation, Na+ or C1-uptake was reduced by only 9-12%. A similar inhibition of D-[3H]mannitol uptake (10-17%) suggests this was due to a nonspecific decrease in the membrane permeability. Other cations such as Ba2+ and Mg2+ had no effect, but La3+ inhibited Na+ and Cl-uptake to the same degree as Ca2 . Calmodulin (2 pM) in combination with Ca2+ (1 ,uM, free concentration) significantly inhibited Na+ uptake when Cl-was the anion by 21-32% and C1-uptake when Na' was the cation by 20-27%. This effect was completely reversed by 10 IAM trifluoperazine. When gluconate was the anion or when choline was the cation, Na+ or Cl-uptake was unaffected by Ca2+/calmodulin and trifluoperazine. The 14 for Ca2+ inhibition of Cl--coupled Na+ uptake was reduced from 200 pAM to 0.2 pAM by incubation with 20 pM calmodulin. The 1; for exogenously added calmodulin studied at 1 ,uM Ca2+ was 0.2 pmM. The K, for trifluoperazine inhibition of the Ca2+/calmodulin response was 3 ,uM. These results represent compelling evidence for intracellular Ca2+/calmodulin regulation of coupled NaCl transport across the intestinal microvillus membrane. The exact mechanism of this regulation remains to be delineated.Recent in vitro studies of intestine indicate a role for intracellular calcium in the regulation of basal and stimulated active electrolyte transport. Alterations in serosal solution Ca2' concentration change Na+ and Cl-fluxes in a fashion that cannot be ascribed to modifications of epithelial passive permeability (1-4). Calcium deprivation increases Na+ and Cl-absorption, whereas high Ca2' concentrations inhibit Na+ and Cl-absorption, cause Cl-secretion, or both. The effect of Ca2" deprivation is reproduced by the Ca2"-channel blocker verapamil (1). Furthermore, NaCl absorption is inhibited or Cl-secretion is stimulated by the Ca2" ionophore A23187 (3, 4), by serotonin (5), and by carbamoylcholine (3) only if Ca2+ is present in the serosal solution. The serotonin effect is also prevented by verapamil (5).Calmodulin may be necessary for Ca2+-regulated transport. This protein has been identified in the intestinal microvillus, where it is primarily associated with the microfilament core (6, 7). Indirect evidence for calmodulin-mediated transport comes from inhibition of electrolyte secretion by trifluoperazine (TFP) (8,9). However, the concentration of TFP necessary in whole gut for such an effect (100-500 ,tM) is far above that reported for other Ca2+/calmodulin-dependent processes (10, 11).The mechanism of calcium's effect is not known, but...

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Calcium dependence of basal electrolyte transport in rabbit ileum

Cited by 35 publications

References 0 publications

Elevated intracellular Ca2+ acts through protein kinase C to regulate rabbit ileal NaCl absorption. Evidence for sequential control by Ca2+/calmodulin and protein kinase C.

Elevated intracellular Ca2+ acts through protein kinase C to regulate rabbit ileal NaCl absorption. Evidence for sequential control by Ca2+/calmodulin and protein kinase C.

Dopamine Stimulation of Active Na and Cl Absorption in Rabbit Ileum

Calcium/calmodulin inhibition of coupled NaCl transport in membrane vesicles from rabbit ileal brush border.

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