Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0043167 (pertussis)
 19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Low concentrations of angiotensin II (Ang II) increase, whereas high concentrations inhibit the apical Na/H antiporter activity in the proximal tubule, but the respective roles of the different signaling pathways in mediating these effects remains unsettled. We studied the effects of both low and high doses of Ang II in the presence of selective signaling pathway inhibitors, on the apical Na/H antiport activity of rat proximal tubule. Experiments were carried out in intact cells of freshly prepared tubule fragments obtained from the outer third of cortex, that is, devoid of basolateral Na/H antiport activity in the absence of bicarbonate transport and H(+)-ATPase activity. In tubules acid-loaded by an NH4Cl prepulse, Na/H antiport activity was assessed by the initial rate of intracellular pH recovery (dpHi/dt), measured with BCECF. When tubules were preincubated with low dose Ang II (10(-11) M for 3 min), dpHi/dt increased by 25 +/- 8%, whereas incubation with high dose Ang II (10(-7) M for 3 min) decreased dpHi/dt by 30 +/- 4%, compared to control (P < 0.01 in both cases). Both effects were abolished in the presence of 2.10(-3) M amiloride. Low dose Ang II-induced increase in dpHi/dt was not affected by preincubation with a specific PKA inhibitor, Rp-CPT-cAMP 10(-4) M, and was completely abolished by preincubation with PKC inhibitors, staurosporine 10(-7) M, sphingosine 5.10(-6) M, or calphostin 10(-6) M. In addition, pretreatment of rats with pertussis toxin led to a partial inhibition of the effect of low dose Ang II. The high dose-Ang II-induced decrease in dpHi/dt was not affected by pretreatment with a calcium-calmodulin kinase inhibitor W-7 10(-4) M. Conversely, pretreatment with the cytochrome P-450 inhibitor econazole 10(-5) M reversed the inhibitory effect of high dose Ang II to a stimulatory effect (24 +/- 8%, P < 0.01), quantitatively similar to the effect of low dose Ang II. In addition, arachidonate was found to exert an econazole-sensitive dose-dependent inhibitory effect on dpHi/dt, and 5,6-EET 10(-6) M, a cytochrome P-450 derived-arachidonic acid metabolite, induced a 38 +/- 9% inhibition, similar to that observed with high dose Ang II alone. There was no additive effect of 5,6-EET and high dose Ang II. Finally, pretreatment with two PLA2 inhibitors (BromoPhenacylBromide, 6.10(-6) M, and oleyloxyethyl phosphorylcholine, 5.10(-6) M) reversed the inhibitory effect of high dose Ang II to a stimulatory effect (32 +/- 11% and 25 +/- 11%, respectively, P < 0.05 for both inhibitors). We conclude that, in intact rat proximal cells, low dose Ang II stimulates the apical Na/H antiport through a pertussis toxin-sensitive G protein-dependent PKC pathway, whereas high dose Ang II inhibits the Na/H antiport activity through the PLA2- and cytochrome P-450-dependent metabolites of arachidonate.
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PMID:Signaling pathways in the biphasic effect of angiotensin II on apical Na/H antiport activity in proximal tubule. 891 15

Protein kinase A (PKA)- and G protein-mediated regulation of immunopurified adult rabbit alveolar epithelial type II (ATII) cell proteins that exhibit amiloride-sensitive Na+ channel activity was studied in planar lipid bilayers and freshly isolated ATII cells. Addition of the catalytic subunit of PKA + ATP increased single channel open probability from 0.42 +/- 0.05 to 0.82 +/- 0.07 in a voltage-independent manner, without affecting unitary conductance. This increase in open probability of the channels was mainly due to a decrease in the time spent by the channel in its closed state. The apparent inhibition constant for amiloride increased from 8.0 +/- 1.8 microM under control conditions to 15 +/- 3 microM after PKA-induced phosphorylation; that for ethylisopropylamiloride increased from 1.0 +/- 0.4 to 2.0 +/- 0.5 microM. Neither pertussis toxin (PTX) nor guanosine 5'-O-(3-thiotriphosphate) affected ATII Na+ channel activity in bilayers. Moreover, PTX failed to affect amiloride-inhibitable 22Na+ uptake in freshly isolated ATII cells. In vitro, ADP ribosylation induced by PTX revealed the presence of a specifically ribosylated band at 40-45 kDa in the total solubilized ATII cell protein fraction, but not in the immunopurified fraction. Moreover, the immunopurified channel was downregulated in response to guanosine 5'-O-(3-thiotriphosphate)-mediated activation of the exogenous G alpha(i-2), but not G(oA), G alpha(i-1), or G alpha(i-3), protein added to the channel. This effect occurred only in the presence of actin. These results suggest that amiloride-sensitive Na+ channels in adult alveolar epithelia regulated by PKA-mediated phosphorylation also retain the ability to be regulated by G alpha([i-2), but not G alpha([i-1) or G alpha(i-3), protein.
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PMID:Protein kinase A phosphorylation and G protein regulation of type II pneumocyte Na+ channels in lipid bilayers. 914 51

Endothelin-1 (ET-1) is a 21-amino acid peptide hormone released from myocardial and endothelial cells, whose receptors (both ETA and ETB are expressed in the myocardium. We report here that ET-1 inhibits the cardiac delayed rectifier K+ current (IK) via a pertussis toxin (PTX)-sensitive mechanism. Ventricular myocytes enzymatically isolated from guinea pig hearts were voltage-clamped by the conventional whole-cell and nystatin-perforated patch technique (intrapipette and extrapipette K+ concentrations, 150 and 5.4 mmol/L, respectively) in the presence of nifedipine (2 mumol/L). Amplitudes of tail and steady state (2-second pulse) currents were measured as IK. ET-1 suppressed the basal IK by 20.9 +/- 2.3% in a concentration-dependent manner, with an IC50 of 1.1 +/- 0.3 nmol/L (n = 19), although it did not suppress the basal IK using the nystatin method. E-4031 (5 mumol/L), a blocker of the rapid component of IK (IKr), did not prevent the inhibitory action of ET-1. ET-1 reduced by 63.4 +/- 6.5% the slow component of IK (IKs) that had been enhanced to approximately 2-fold by isoproterenol (ISO, 20 nmol/L). The action was concentration dependent, with an IC50 of 0.7 +/- 0.4 nmol/L (n = 22), and was also observed using the nystatin method. The effect of ET-1 appeared to be mediated by an ETA receptor, because it was prevented by FR139317, an ETA-selective antagonist (1 mumol/L, n = 4), and sarafotoxin s6c, an ETB-selective agonist (100 nmol/L, n = 4), could not inhibit the ISO-enhanced IK. ET-1 antagonized IKs enhanced by histamine (250 nmol/L, n = 7) and forskolin (500 nmol/L, n = 7) but did not inhibit IKs enhanced by the internal application of cAMP (100 mumol/L, n = 6). Preincubation of myocytes with PTX (5 micrograms/mL for > 60 minutes at 36 degrees C) completely abolished the inhibitory action of ET-1 on the ISO-enhanced IKs (n = 4). Thus, nanomolar ET-1 inhibits IKs via the ETA receptor/PTX-sensitive G protein/PKA pathway.
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PMID:Endothelin-1 inhibits the slow component of cardiac delayed rectifier K+ currents via a pertussis toxin-sensitive mechanism. 924 82

A perforated-patch whole-cell recording method was used to determine whether nitric oxide signaling participates in acetylcholine (ACh)-induced regulation of basal L-type Ca2+ current (ICa,L) in cat atrial myocytes. Exposure to 1 microM ACh for 2 min inhibited basal ICa,L (-21 +/- 3%), and withdrawal of ACh elicited rebound stimulation of ICa,L above control (80 +/- 13%) (n = 23). Stimulation of ICa,L elicited by withdrawal of ACh (but not ACh-induced inhibition of ICa,L) was blocked by either 50 microM hemoglobin; 30 microM ODQ or 10 microM methylene blue, inhibitors of soluble guanylate cyclase; 10 microM W-7, a calmodulin inhibitor; or 10 microM L-NIO, an inhibitor of constitutive NO synthase (NOS). In cells incubated in 5 mM L-arginine, ACh-induced rebound stimulation of ICa,L was enhanced compared with control responses. Histochemical assay (NADPH diaphorase) indicated that atrial myocytes express constitutive NOS. NO-donor, spermine/NO (SP/NO), >1 microM stimulated basal ICa,L. SP/NO-induced stimulation of ICa,L was inhibited by 50 microM hemoglobin, 30 microM ODQ, or 5 microM H-89, an inhibitor of PKA, and was unchanged by 50 microM MnTBAP, a peroxynitrite scavenger. When ICa,L was prestimulated by 10 microM milrinone, an inhibitor of cGMP-inhibited phosphodiesterase (type III) activity, SP/NO failed to further increase ICa,L. In cells incubated in pertussis toxin (3.4 microg/ml for 6 h; 36 degrees C), ACh failed to affect ICa,L, but 100 microM SP/NO or 10 microM milrinone still increased basal ICa,L. These results indicate that in cat atrial myocytes NO signaling mediates stimulation of ICa,L elicited by withdrawal of ACh but not ACh-induced inhibition of basal ICa,L. NO activates cGMP-induced inhibition of phosphodiesterase (type III) activity. Upon withdrawal of ACh, this mechanism allows cAMP to recover to levels above control, thereby stimulating ICa,L. Pertussis toxin-sensitive G-proteins couple M2 muscarinic receptors to NO signaling. NO-mediated stimulation of ICa, L elicited by withdrawal of ACh may be an important mechanism that rapidly restores cardiac pacemaker and contractile functions after cholinergic suppression of atrial activity.
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PMID:Nitric oxide signaling mediates stimulation of L-type Ca2+ current elicited by withdrawal of acetylcholine in cat atrial myocytes. 941 39

Peptones are potent stimulants of cholecystokinin (CCK) release in rats, both in vivo and ex vivo in a model of isolated vascularly perfused duodeno-jejunum preparation and in vitro in the intestinal CCK-producing cell line STC-1. The underlying mechanisms were here investigated with this cell line. Protein hydrolysates from various origins (meat, casein, soybean, and ovalbumin; 0.5-1%, wt/vol) dose dependently increased CCK release. Cephalosporin antibiotics, which mimic tripeptides, also stimulated the release of CCK over the concentration range 1-20 mM. The study of concentration dependence of cephalosporin uptake indicated a passive diffusion process at either pH 7.4 or pH 6.0, thus arguing against the involvement of a peptide transporter in CCK secretion. After pertussis toxin treatment (200 ng/ml; 5 h), the peptone- and cephalexin-induced CCK secretion was significantly reduced, suggesting the involvement of pertussis toxin-sensitive heterotrimeric G protein(s) in the secretory activity of STC-1 cells. Consistent with this was the identification by Western blot of G(i2)alpha, G(i3)alpha, and G(o)alpha immunoreactivities in STC-1 cell extracts. Additionally, peptones and cephalexin increased the cellular content in inositol phosphates, whereas a mild increase in cAMP content was restricted to peptone-treated cells. Protein kinase A or C inhibition did not modify peptone- or antibiotic drug-evoked CCK release. The extracellular Ca2+ chelator EGTA (500 microM) and the intracellular Ca2+ chelator BAPTA-AM [1,2-bis-(O-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl) ester; 20 microM] abolished the peptone- and antibiotic drug-induced CCK release. Nifedipine and verapamil (10 microM) reduced by about 50% the CCK secretion evoked by these two secretagogues. In conclusion, peptones and some cephalosporins are potent stimulants of CCK release in the STC-1 cell line. The cellular mechanisms involve pertussis toxin-sensitive G protein(s) and are dependent on Ca2+ availability. We suggest that the STC-1 cell line is a useful model to study the molecular basis of peptone-induced CCK secretion.
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PMID:Regulation of cholecystokinin secretion by peptones and peptidomimetic antibiotics in STC-1 cells. 949 22

Formylated peptides (e.g. n-formyl-Met-Leu-Phe (fMLP)) and platelet-activating factor (PAF) mediate chemotactic and cytotoxic responses in leukocytes through receptors coupled to G proteins that activate phospholipase C (PLC). In RBL-2H3 cells, fMLP utilizes a pertussis toxin (ptx)-sensitive G protein to activate PLC, whereas PAF utilizes a ptx-insensitive G protein. Here we demonstrate that fMLP, but not PAF, enhanced intracellular cAMP levels via a ptx-sensitive mechanism. Protein kinase A (PKA) inhibition by H-89 enhanced inositol phosphate formation stimulated by fMLP but not PAF. Furthermore, a membrane-permeable cAMP analog 8-(4-chlorophenylthio)-cAMP (cpt-cAMP) inhibited phosphoinositide hydrolysis and secretion stimulated by fMLP but not PAF. Both cpt-cAMP and fMLP stimulated PLCbeta3 phosphorylation in intact RBL cells. The purified catalytic subunit of PKA phosphorylated PLCbeta3 immunoprecipitated from RBL cell lysate. Pretreatment of intact cells with cpt-cAMP and fMLP, but not PAF, resulted in an inhibition of subsequent PLCbeta3 phosphorylation by PKA in vitro. These data demonstrate that fMLP receptor, which couples to a ptx-sensitive G protein, activates both PLC and cAMP production. The resulting PKA activation phosphorylates PLCbeta3 and appears to block the ability of Gbetagamma to activate PLC. Thus, both fMLP and PAF generate stimulatory signals for PLCbeta3, but only fMLP produces a PKA-dependent inhibitory signal. This suggests a novel mechanism for the bidirectional regulation of receptors which activate PLC by ptx-sensitive G proteins.
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PMID:Differential regulation of formyl peptide and platelet-activating factor receptors. Role of phospholipase Cbeta3 phosphorylation by protein kinase A. 955 82

The effects of adenosine on the voltage-sensitive delayed-rectifier K+ (IK) currents and hyperpolarization-activated cationic inward current (Ih) were studied in cultured frog melanotrophs using the whole-cell configuration of the patch-clamp technique. The A1 receptor agonist R-N6-phenylisopropyl-adenosine (R-PIA; 50 microM) reversibly increased IK. Perfusion of dibutyryl-cAMP (1 mM) in the external solution did not modify the R-PIA-induced enhancement of IK. Pretreatment of melanotrophs with pertussis toxin (1 microg/ml; 12 h) totally abolished the R-PIA-evoked response. Application of hyperpolarizing voltage pulses from -60 to -120 mV to melanotrophs induced a two-component inward current corresponding to an Ih-like conductance. This conductance was characterized by a high K+ selectivity and a low Na+ permeability and was resistant to tetrodotoxin (1 microM). R-PIA had no effect on Ih. The present study demonstrates that in frog melanotrophs adenosine inhibits the electrical activity by activating IK through an A1 receptor subtype coupled to a pertussis toxin-sensitive pathway independent of the cAMP/PKA system. This study also demonstrates the existence of a Ih conductance in frog melanotrophs which is not modulated by A1 receptors.
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PMID:Adenosine potentiates the delayed-rectifier potassium conductance but has no effect on the hyperpolarization-activated Ih current in frog melanotrophs. 963 Jun 70

1. The effect of the non-steroidal anti-inflammatory drugs naproxen, mefenamic acid, phenylbutazone, piroxicam and tolmetin on the vanadate (0.3 mM)-induced tonic contraction, as well as the modifications of these effects by the G-protein inhibitor pertussis toxin, and the inhibitors of protein kinase A, Rp-cAMPS (Rp-Adenosine 3',5'-cyclic monophosphothioate triethylamine salt) and protein kinase C, H-7 [1(5-isoquinolynilsulfonyl)-2-methyl-piperazine], have been assayed to study the possible nature of intracellular mediators contributing to the inhibitory effects of NSAIDs in rat uterine smooth muscle incubated in medium lacking calcium plus EDTA. The effect of phorbol 12,13-dibutyrate on vanadate contraction and its modification with H-7 has also been examined. 2. Naproxen (6-600 microM), mefenamic acid (6-300 microM), phenylbutazone (6-300 microM), piroxicam (6-600 microM) and tolmetin (6-600 microM) produced concentration-dependent relaxation of vanadate-induced tonic contraction. The potency order, in accordance with their respective IC50 values was: phenylbutazone > or = mefenamic acid > or = naproxen > tolmetin > or = piroxicam. 3. The relaxant effects of naproxen, phenylbutazone, piroxicam and tolmetin were significantly antagonized with pertussis toxin (50 ng ml-1), Rp-cAMPS (100 microM) and H-7 (1 microM). However, the effect of mefenamic acid was unmodified by the three drugs. This suggests that the effect of mefenamic acid and other NSAIDs occur by different mechanisms. 4. Phorbol 12,13-dibutyrate relaxed the vanadate contraction but the maximal relaxation achieved (54.8 +/- 8.3%, n = 4) was lower than those induced with the NSAIDs. On the other hand, H-7 (1 microM) did not modify the relaxant effect of phorbol 12,13-dibutyrate. This suggests that H-7 behaves as a PKA, but not a PKC inhibitor, under the present experimental conditions. 5. The relaxation by naproxen, phenylbutazone, piroxicam and tolmetin is presumably produced by increasing cAMP because the effects of these are antagonized with Rp-cAMPS and H-7, and by pertussis-toxin-sensitive mechanisms.
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PMID:Contribution of cAMP to the inhibitory effect of non-steroidal anti-inflammatory drugs in rat uterine smooth muscle. 972 23

GH, in the presence of glucocorticoid, produces a delayed increase in lipolysis in rat adipose tissue, but the biochemical mechanisms that account for this action have not been established. Other lipolytic agents rapidly activate adenylyl cyclase (AC) and the resulting production of cAMP initiates a chain of reactions that culminates in the activation of hormone-sensitive lipase. We compared responses of segments of rat epididymal fat or isolated adipocytes to 30 ng/ml GH and 0.1 microg/ml dexamethasone (Dex) with 0.1 ng/ml isoproterenol (ISO), which evoked a similar increase in lipolysis. All measurements were made during the fourth hour after the addition of GH+Dex or immediately after the addition of ISO to cells or tissues that had been preincubated for 3 h without hormone. Although no significant increases in cAMP were discernible in homogenates of GH+Dex-treated tissues, Rp-cAMPS (Rp-adenosine 3'5'-phosphothioate), a competitive inhibitor of cAMP, was equally effective in decreasing lipolysis induced by GH+Dex or ISO. The proportion of PKA that was present in the active form was determined by measuring the incorporation of 32P from [gamma-32P]ATP into kemptide in the absence and presence of saturating amounts of cAMP. GH+Dex and ISO produced similar increases in protein kinase A activity in tissue extracts. Treatment with GH+Dex did not change the total forskolin-stimulated AC present in either a crude membrane pellet sedimented at 16K x g or a less dense membrane pellet sedimented at 100K x g, but doubled the AC activity in the 16K pellet when assayed in the absence of forskolin. To evaluate possible effects on G proteins, pellets obtained from centrifugation of adipocyte homogenates at 16K x g and 100K x g were solubilized and subjected to PAGE and Western analysis. GH+Dex decreased Gi alpha2 by 44% (P < 0.02) in the 16K pellets and increased it by 52% (P < 0.01) in the 100K pellets. Gs alpha in the 16K pellet was unaffected by GH+Dex and was decreased (P < 0.05) in the 100K pellet. Sucrose density fractionation of the 16K pellets revealed a similar GH+Dex-dependent shift of Gi alpha2 to less dense fractions as determined by both Western analysis and [32P]NAD ribosylation catalyzed by pertussis toxin. No such changes were seen in the distribution of Gs alpha or 5'-nucleotidase. Colchicine (100 microM) blocked the GH+Dex-dependent shift of Gi alpha2 from the 16K to the 100K pellet and blocked the lipolytic effects of GH+Dex, but not those of ISO. We conclude that by modifying the relationship between AC and Gi alpha2, GH+Dex relieves some inhibition of cAMP production and consequently increases lipolysis.
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PMID:Growth hormone and dexamethasone stimulate lipolysis and activate adenylyl cyclase in rat adipocytes by selectively shifting Gi alpha2 to lower density membrane fractions. 1006 47

Glutamate is the primary excitatory transmitter in the suprachiasmatic nucleus (SCN). Ionotropic glutamate receptors (iGluRs) mediate transduction of light information from the retina to the SCN, an important circadian clock phase shifting pathway. Metabotropic glutamate receptors (mGluRs) may play a significant modulatory role. mGluR modulation of SCN responses to glutamate was investigated with fura-2 calcium imaging in SCN explant cultures. SCN neurons showed reproducible calcium responses to glutamate, kainate, and N-methyl-D-aspartate (NMDA). Although the type I/II mGluR agonists L-CCG-I and t-ACPD did not evoke calcium responses, they did inhibit kainate- and NMDA-evoked calcium rises. This interaction was insensitive to pertussis toxin. Protein kinase A (PKA) activation by 8-bromo-cAMP significantly reduced iGluR inhibition by mGluR agonists. The inhibitory effect of mGluRs was enhanced by activating protein kinase C (PKC) and significantly reduced in the presence of the PKC inhibitor H7. Previous reports show that L-type calcium channels can be modulated by PKC and PKA. In SCN cells, about one-half of the calcium rise evoked by kainate or NMDA was blocked by the L-type calcium channel antagonist nimodipine. Calcium rises evoked by K+ were used to test whether mGluR inhibition of iGluR calcium rises involved calcium channel modulation. These calcium rises were primarily attributable to activation of voltage-activated calcium channels. PKC activation inhibited K+-evoked calcium rises, but PKC inhibition did not affect L-CCG-I inhibition of these rises. In contrast, 8Br-cAMP had no effect alone but blocked L-CCG-I inhibition. Taken together, these results suggest that activation of mGluRs, likely type II, modulates glutamate-evoked calcium responses in SCN neurons. mGluR inhibition of iGluR calcium rises can be differentially influenced by PKC or PKA activation. Regulation of glutamate-mediated calcium influx could occur at L-type calcium channels, K+ channels, or at GluRs. It is proposed that mGluRs may be important regulators of glutamate responsivity in the circadian system.
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PMID:Metabotropic glutamate receptor modulation of glutamate responses in the suprachiasmatic nucleus. 1008 57


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