Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.1.1 (hexokinase)
 5,274 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Using equivalent short circuit current (ISC) measurements we examined the effect of extracellular ATP on transepithelial ion transport in M-1 mouse cortical collecting duct cells. Apical addition of ATP produced a rapid transient peak increase in ISC. This was followed by a fall below basal ISC due to a reduction in the amiloride-sensitive ISC component. 2. The ATP-induced ISC increase was preserved in the presence of apical amiloride while it was reduced in the absence of extracellular Cl- and in the presence of the apical Cl- channel blockers diphenylamine-2-carboxylic acid (DPC, 1 mM), DIDS (300 microM) and niflumic acid (100 microM). 3. The stimulatory effect of apical ATP on ISC was concentration dependent with an EC50 of about 0.6 microM. Basolateral ATP elicited a similar ISC response. Experiments using the ATP scavenger hexokinase demonstrated that the ATP effects were elicited via separate apical and basolateral receptors. 4. ATP and UTP applied to either the apical or the basolateral bath equi-potently stimulated ISC while 'purified' ADP and UDP had no effect consistent with P2Y2 purinoceptors, the expression of which was confirmed using RT-PCR. 5. Intracellular calcium concentration ([Ca2+]i) measurements using fura-2 demonstrated that ATP and UTP elicited a rise in [Ca2+]i with EC50 values of 1.1 and 0.6 microM, respectively. The shape and time course of the calcium response were similar to those of the ISC response. The peak ISC response was preserved in the nominal absence of extracellular calcium but was significantly reduced in cells pre-incubated with the calcium chelator BAPTA AM. 6. We conclude that in M-1 cells extracellular ATP reduces amiloride-sensitive Na+ absorption and stimulates Cl- secretion via calcium-activated Cl- channels through activation of P2Y2 purinoreceptors located in the apical and basolateral membrane.
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PMID:ATP stimulates Cl- secretion and reduces amiloride-sensitive Na+ absorption in M-1 mouse cortical collecting duct cells. 1074 85

In cystic fibrosis airway epithelia, mutation of the CFTR protein causes a reduced response of Cl(-) secretion to secretagogues acting via cAMP. Using a Ca(2+) imaging system, the hypothesis that CFTR activation may permit ATP release and regulate [Ca(2+)](i) via a receptor-mediated mechanism, is tested in this study. Application of external nucleotides produced a significant increase in [Ca(2+)](i) in normal (16HBE14o(-) cell line and primary lung culture) and in cystic fibrosis (CFTE29o(-) cell line) human airway epithelia. The potency order of nucleotides on [Ca(2+)](i) variation was UTP >> ATP > UDP > ADP > AMP > adenosine in both cell types. The nucleotide [Ca(2+)](i) response could be mimicked by activation of CFTR with forskolin (20 microm) in a temperature-dependent manner. In 16HBE14o(-) cells, the forskolin-induced [Ca(2+)](i) response increased with increasing temperature. In CFTE29o(-) cells, forskolin had no effect on [Ca(2+)](i) at body temperature-forskolin-induced [Ca(2+)](i) response in CF cells could only be observed at low experimental temperature (14 degrees C) or when cells were cultured at 26 degrees C instead of 37 degrees C. Pretreatment with CFTR channel blockers glibenclamide (100 microm) and DPC (100 microm), with hexokinase (0.5 U/mg), and with the purinoceptor antagonist suramin (100 microm), inhibited the forskolin [Ca(2+)](i) response. Together, these results demonstrate that once activated, CFTR regulates [Ca(2+)](i) by mediating nucleotide release and activating cell surface purinoceptors in normal and CF human airway epithelia.
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PMID:CFTR regulation of intracellular calcium in normal and cystic fibrosis human airway epithelia. 1101 59