Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.6.1.1 (adenylate cyclase)
 19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Many of the hormone-regulated ion transport processes in distal nephron involve transcellular pathways which require a passive entry of ions at the apical membrane of the distal tubule cells. To investigate molecular mechanisms underlying the ionic permeability of the distal tubule apical membrane, a study was undertaken in which vesicles prepared from apical membranes from isolated rabbit distal tubules were fused onto a planar lipid bilayer. These experiments led to the identification of several ionic channels including a Cl(-)-permeable channel of 14 pS with a Na+ over Cl- permeability ratio, PNa/PCl < 0.09. The open channel probability (Po) showed a weak voltage dependency with Po increasing slightly at negative potential values (intracellular (trans) relative to extracellular (cis) for right-side-out vesicles). Channel activity was inhibited by NPPB at high concentrations (> 100 microM) and by DIDS (300 microM). A small inhibitory effect was also observed in the presence of DPC at concentrations ranging from 200 microM to 500 microM. The presence of SO4(2-) (32 mmol/l) in the trans solution caused a complete inhibition of channel activity, but no modification of channel behaviour was observed with the non-selective channel blocking agent gadolinium (Gd3+) at 100 microM. Finally, addition of the catalytic subunit of protein kinase A into the trans chamber (60 U/ml to 80 U/ml) led to an increase in channel activity characterized by a greater number of active channels coupled to an increase of the individual channel open probability. The action of the protein kinase A could be cancelled by the addition of a non specific protein phosphatase, such as alkaline phosphatase. Our results suggest that the apical membrane of the rabbit distal tubule contains a Cl- permeable channel of small conductance the activity of which may be modulated by hormones linked to the adenylate cyclase pathway.
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PMID:Evidence from incorporation experiments for an anionic channel of small conductance at the apical membrane of the rabbit distal tubule. 897 99

Increase in intracellular adenosine 3', 5'-cyclic monophosphate (cAMP) is a common pathway for many clinically used drugs to cause pulmonary artery (PA) relaxation. Activity of sarcolemmal K+ and Cl(-)-channels is an important determinant of membrane potential (Em), which, in turn, plays a critical role in regulating pulmonary vascular tone. Whether K+ and Cl- channels were involved in cAMP-induced PA relaxation was tested using isolated rat PA rings. Raising extracellular K+ concentration from 20 to 142.7 mM increased the K(+)-evoked contraction, but significantly decreased the relaxation induced by the adenylate cyclase activator, forskolin (FSK, 2.5 microM), suggesting that FSK-induced PA relaxation depended on transmembrane K+ gradient. Indeed, the FSK-induced relaxation was inhibited by 4-aminopyridine (4-AP, 10 mM), a voltage-gated K+ (Kv) channel blocker. Neither the Ca(2+)-activated K+ channel blocker, charybdotoxin, nor the ATP-sensitive K+ channel blocker, glibenclamide, had this effect. Furthermore, reducing extracellular Cl- concentration from 142.7 to 50 mM significantly decreased the FSK-induced relaxation in PA rings precontracted with 142.7 mM K+ (Ek approximately 0 mV), but negligibly affected the evoked contraction. This indicates that transmembrane Cl- gradient also regulates FSK-induced PA relaxation. Indeed, the Cl- channel blocker, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB, 10 microM), significantly inhibited the FSK-induced relaxation in PA rings preconstricted by 142.7 mM K+. In summary, the data suggest that the cAMP-induced PA relaxation is attributable, at least partly, to both activation of the 4-AP-sensitive Kv channels and stimulation of the NPPB-sensitive Cl- channels.
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PMID:Roles of K+ and Cl- channels in cAMP-induced pulmonary vasodilation. 945 70

X-ray microanalysis was used to investigate whether cAMP- and/or Ca2+-activated regulation of chloride and potassium efflux is expressed in primary cultures of sweat gland duct cells. The effects of extracellular UTP and ATP on the duct cells, and the signalling system involved in the response to ATP was also studied. Primary cultures from duct cells of human sweat glands responded to 1 microM carbachol, 2 microM of the Ca2+ ionophore A23187, or 5 mM 8-bromo-cAMP stimulation for 5 min, resulting in a decrease in cellular Cl and K concentrations. 50 microM 5-nitro-2-(3-phenylpropyl-amino)-benzoic acid (NPPB), a Cl- channel blocker, can inhibit the decrease in Cl concentration induced by cAMP. Extracellular (200 microM) ATP caused a decrease of Cl and K in cultured duct cells, while (200 microM and 2 mM) UTP was ineffective. Both the phosphoinositidase C inhibitor U73122 (10 microM) and the absence of extracellular Ca2+ abolished the ATP-induced decrease in Cl and K content. Alloxan (1.25 mM), an adenylate cyclase inhibitor, had an inhibitory effect on the response to ATP. The decrease in K, but not in Cl, content in the cells elicited by ATP was blocked by prior incubation with 100 ng/ml pertussis toxin, indicating the coupling of ATP to pertussis toxin-sensitive G-proteins. In conclusion, both Ca2+- and cAMP-dependent Cl- permeability is present in primary cultures from duct cells of human sweat gland. The response to ATP can be mediated both by Ca2+- and by cAMP-dependent pathways, and is coupled to pertussis toxin-sensitive G-proteins.
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PMID:Regulation of ion content in primary cultures from reabsorptive ducts of human sweat glands studied by X-ray microanalysis. 987 64

We investigated the effects of 5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one(DCEBIO) on the Cl- secretory response of the mouse jejunum using the Ussing short-circuit current (Isc) technique. DCEBIO stimulated a concentration-dependent, sustained increase in Isc (EC50 41 +/- 1 microM). Pretreating tissues with 0.25 microM forskolin reduced the concentration-dependent increase in Isc by DCEBIO and increased the EC50 (53 +/- 5 microM). Bumetanide blocked (82 +/- 5%) the DCEBIO-stimulated Isc consistent with Cl- secretion. DCEBIO was a more potent stimulator of Cl- secretion than its parent molecule, 1-ethyl-2-benzimidazolinone. Glibenclamide or NPPB reduced the DCEBIO-stimulated Isc by >80% indicating the participation of CFTR in the DCEBIO-stimulated Isc response. Clotrimazole reduced DCEBIO-stimulated Isc by 67 +/- 15%, suggesting the participation of the intermediate conductance Ca2+-activated K+ channel (IKCa) in the DCEBIO-activated Isc response. In the presence of maximum forskolin (10 microM), the DCEBIO response was reduced and biphasic, reaching a peak response of the change in Isc of 43 +/- 5 microA/cm2 and then falling to a steady-state response of 17 +/- 10 microA/cm2 compared with DCEBIO control tissues (61 +/- 6 microA/cm2). The forskolin-stimulated Isc in the presence of DCEBIO was reduced compared with forskolin control tissues. Similar results were observed with DCEBIO and 8-BrcAMP where adenylate cyclase was bypassed. H89, a PKA inhibitor, reduced the DCEBIO-activated Isc, providing evidence that DCEBIO increased Cl- secretion via a cAMP/PKA-dependent manner. These data suggest that DCEBIO stimulates Cl- secretion of the mouse jejunum and that DCEBIO targets components of the Cl- secretory mechanism.
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PMID:DCEBIO stimulates Cl- secretion in the mouse jejunum. 1613 45

The present study investigated whether cAMP-dependent cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel current (i.e., I(Cl.CFTR) or I(Cl.cAMP)) would be expressed in pig cardiac myocytes using whole-cell patch technique and reverse transcription polymerase chain reaction (RT-PCR). It was found that the beta-adrenoceptor agonist isoproterenol activated a time-independent current in myocytes from the ventricle, but not the atrium of pig heart. Histamine and forskolin (an adenylate cyclase activator) induced a similar current in pig ventricular cells. The current induced by isoproterenol was blocked by the PKA inhibitor H-7, reduced by the replacement of external Cl(-) ion, and inhibited by the application of 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB), but not 4'-diisothiocynatostilbene-2,2'-disulfonic acid (DIDS), typical of I(Cl.CFTR). I(Cl.CFTR) showed a small difference in regional myocytes across the left ventricular wall from epicardium to endocardium. Isoproterenol-induced current was 3.1+/-0.2 (n=33), 2.8+/-0.2 (n=25) and 2.3+/-0.2 pA/pF (n=31) respectively in subepicardial, midmyocardial, and subendocardial myocytes (P<0.05, subepicardium vs. subendocardium). RT-PCR and Western blotting analysis revealed that significant differences in CFTR channel mRNA and protein levels were present in atrial and ventricular cells, but not in regional ventricular cells across the ventricular wall from subepicardium to subendocardium. These results indicate that the functional CFTR channel (i.e., I(Cl.CFTR)) is present in ventricular myocytes, but not in atrial cells of pig heart.
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PMID:Evidence for cystic fibrosis transmembrane conductance regulator chloride current in swine ventricular myocytes. 1711 38

Heme induces Cl(-) secretion in intestinal epithelial cells, most likely via carbon monoxide (CO) generation. The major source of endogenous CO comes from the degradation of heme via heme oxygenase (HO). We hypothesized that an inhibitor of HO activity, tin protoporphyrin (SnPP), may inhibit the stimulatory effect of heme on Cl(-) secretion. To test this hypothesis, we treated an intestinal epithelial cell line (Caco-2 cells) with SnPP. In contrast to our expectations, Caco-2 cells treated with SnPP had an increase in their short-circuit currents (I(sc)) in Ussing chambers. This effect was observed only when the system was exposed to ambient light. SnPP-induced I(sc) was caused by Cl(-) secretion because it was inhibited in Cl(-)-free medium, with ouabain or 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB). The Cl(-) secretion was not via activation of the CFTR, because a specific inhibitor had no effect. Likewise, inhibitors of adenylate cyclase and guanylate cyclase had no effect on the enhanced I(sc). SnPP-induced I(sc) was inhibited by the antioxidant vitamins, alpha-tocopherol and ascorbic acid. Electron paramagnetic resonance experiments confirmed that oxidative reactions were initiated with light in cells loaded with SnPP. These data suggest that SnPP-induced effects may not be entirely due to the inhibition of HO activity but rather to light-induced oxidative processes. These novel effects of SnPP-photosensitized oxidation may also lead to a new understanding of how intestinal Cl(-) secretion can be regulated by the redox environment of the cell.
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PMID:Tin protoporphyrin induces intestinal chloride secretion by inducing light oxidation processes. 1721 23

Bicarbonate secretion occurs in almost all segments of the gastrointestinal tract. This study examined HCO(3)(-) secretion in the ileum, since it is less understood than HCO(3)(-) secretion in other intestinal segments. Mouse ileal mucosa was mounted in vitro in Ussing chambers, and the mucosal alkalinization rate (J(OH)) was determined by pH stat titration, while the mucosal side was bathed with a buffer-free solution (100% O(2)) and the serosal side with a HCO(3)(-)/CO(2)-buffered solution. The transmural potential difference (PD) was recorded. The mucosal alkalinization rate (J(OH)) was higher in the presence of mucosal Cl(-) than in its absence. Forskolin, an activator of adenylate cyclase, enhanced J(OH) and PD in both the presence and absence of mucosal Cl(-). Mucosal SO(4)(2-) also caused an increase in J(OH), although the magnitude was smaller than that induced by Cl(-). Mucosal Cl(-)-dependent J(OH) was partially inhibited by acetazolamide, 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), tenidap and probably also by niflumic acid, but not by glibenclamide, DIDS or bumetanide. The forskolin-induced J(OH) value and PD were both inhibited by NPPB and probably also by tenidap. It is concluded that HCO(3)(-)- secretion in the ileum follows a mucosal Cl(-)-dependent pathway and a cAMP-activated pathway, each being distinct from each other. The Cl(-)-dependent pathway is probably mediated by the slc26a6 anion exchanger, and possibly also by the slc26a3 anion exchanger. The cAMP-activated HCO(3)(-) secretion is probably mediated by the cystic fibrosis transmembrane conductance regulator.
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PMID:pH stat studies on bicarbonate secretion in the isolated mouse ileum. 1800 Mar 36