Properties of soluble ATPase of gastric mucosa II Effect of HCO3−

Blum, A. L.; Shah, Gaurav; Pierre, Thomas St.; Helander, Herbert F.; Sung, Cynthia; Wiebelhaus, Virgil D.; Sachs, George

doi:10.1016/0005-2736(71)90087-3

Cited by 79 publications

(9 citation statements)

References 17 publications

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“…Optimal pH in the choroid plexus was similar to that in rat brain (15), but was higher than that in dog gastric mucosa (14). Participation of HCO3-ATPase in bicarbonate transport in the choroid plexus may be clarified with reference to some characteristics of this enzyme described herein.…”

Section: Discussionmentioning

confidence: 63%

“…Optimal ATP : Mg ratio for Mg-ATPase activity in 8,000 x g and 10,000 x g fractions of choroid plexus was about 1, while a ratio more than 2 is reported for brain (15) and gastric mucosa (7,13). Further, optimal pH for Mg-ATPase in the above-mentioned two fractions was over pH 9.0, while it was around pH 8.5 in other tissues (7,14,15,22). Besides these differences between Mg-ATPase in the choroid plexus and in other tissues, the activity of Mg-ATPase was considerably high in the choroid plexus homogenate, among the tissues examined (choroid plexus, brain, kidney and gastric mucosa).…”

Section: Discussionmentioning

confidence: 84%

See 1 more Smart Citation

Na,K-, Mg- and HCO3-adenosine triphosphatases in the rabbit brain choroid plexus.

et al. 1980

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Section: Discussionmentioning

confidence: 63%

Section: Discussionmentioning

confidence: 84%

Na,K-, Mg- and HCO3-adenosine triphosphatases in the rabbit brain choroid plexus.

et al. 1980

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“…As in the case of other anion-stimulated ATPases there is some reactivity for other trinucleotides, especially ITP and GTP [Blum et al, 1971;Simon and Thomas, 1972;Van Amelsvoort et al, 1977;Gassner and Komnick, 1981b], The activity on the dinucleotide ADP is con trary to previously described anion-sensitive ATPase, but may be explained by the fact that ADP is one of the more abundant organic phosphates in the bovine lens; along with ATP, it makes up the bulk of the highenergy phosphates [Kuck, 1970]. Also, although anion-dependent ATPases do not generally show activity on ADP, some cation-dependent ATPases have been shown to do so.…”

Section: Discussionmentioning

confidence: 99%

Chloride- and Bicarbonate-Stimulated ATPase Activity in Bovine Lens Epithelium

Jose¹,

Gassner²

1983

Ophthalmic Res

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An anion-stimulated, ouabain-insensitive Mg²⁺ATPase activity has been found in fresh homogenates prepared from capsules and epithelia of bovine lenses. Approximately equal activity was observed in the presence of HCO₃^–– or of Cl^––. The stimulation of each anion obeys saturation kinetics, with an optimum at approximately 20 mM Cl^–– or HCO₃^––. Whereas SCN^–– inhibits anion-activated ATPase in most other tissues, it failed to inhibit Cl^–– or HCO₃^––stimulated ATPase activity in the bovine lens. On the contrary, SCN^–– proved a potent activator of the enzyme. However, in keeping with other tissues, OCN^–– and the diuretic drugs, furosemide and ethacrynic acid are inhibitory. ATP is the primary substrate for the enzyme, which also shows some activity on GTP, ITP, and even ADP. Little Na⁺/ K⁺-dependent ATPase activity was observed in the fresh homogenate, but it increased in lyophilized preparations. In contrast, the lyophilized preparations showed no anion-dependent ATPase activity. It is postulated that active bicarbonate ion transport in the lens may be mediated by this anion-dependent ATPase.

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“…If the transport of these ions is not linked to the movement of Na +, how are they able to influence water or fluid secretion? This is an unresolved point for both the ciliary process as well as for tissues with active C1-/HCO3-pumps and HCOa-ATPase, such as the stomach (3,15), pancreas (24), or turtle bladder (22,23). The intracacies of C1-/HCO3-secretion and water movement are not clear.…”

Section: Commentmentioning

confidence: 99%

Bicarbonate ATP-ase in ciliary body and a theory of Diamox effect on aqueous humor formation

Cotlier

1979

Int Ophthalmol

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Bicarbonate was found to stimulate ATP breakdown by rabbit or cat ciliary body-iris homogenates. Maximum HCO3- stimulation of ATPase with Tris-Hepes buffer occured at pH 8.0. Acid pH and chloride ions in the media reduced the activity of the HCO3--stimulated ATPase. The Km for ATP was 0.55 mmolar and for HCO3-, 20 mmlar. HCO3- ATPase was not inhibited by acetazolamide added to in vitro. It is postulated that ATPase represents the linkage step of energy donor mechanism and active CT secretion in acid aqueous humors (human, cat.) or HCO3- secretion in alkaline aqueous humor (rabbit, guinea pig). Inhibition of Cl- or HCO3- secretion by acetazolamide results from decreased intracellular HCO3- levels which, in turn, reduces the stimulation of the HCO3- ATPase.

show abstract

Properties of soluble ATPase of gastric mucosa II Effect of HCO3−

Cited by 79 publications

References 17 publications

Na,K-, Mg- and HCO3-adenosine triphosphatases in the rabbit brain choroid plexus.

Na,K-, Mg- and HCO3-adenosine triphosphatases in the rabbit brain choroid plexus.

Chloride- and Bicarbonate-Stimulated ATPase Activity in Bovine Lens Epithelium

Bicarbonate ATP-ase in ciliary body and a theory of Diamox effect on aqueous humor formation

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