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Patrício Soares-da-Silva

Publications and source records attributed to Patrício Soares-da-Silva.

At least 19 recordsLinked to original sources
PubMed2007

Eslicarbazepine acetate (BIA 2-093).

Eslicarbazepine acetate (ESL) [(S)-(--)-10-acetoxy-10,11-dihydro-5H-dibenz[b,f]azepine-5-carboxamide], formerly known as BIA 2-093, is a novel central nervous system (CNS)-active compound with anticonvulsant activity. It behaves as a voltage-gated sodium channel (VGSC) blocker and is currently under clinical development for the treatment of epilepsy and bipolar disorder. ESL shares with carbamazepine and oxcarbazepine the dibenzazepine nucleus bearing the 5-carboxamide substitute, but is structurally different at the 10,11-position. This molecular variation results in differences in metabolism, preventing the formation of toxic epoxide metabolites such as carbamazepine-10,11 epoxide. In pharmacokinetic studies in humans, ESL was rapidly and extensively metabolized to eslicarbazepine (S-licarbazepine), which is responsible for pharmacological activity. ESL has been tested in patients with refractory partial-onset seizures and was found to be efficacious and well tolerated. Monotherapy studies in adult epileptic patients and add-on studies in epileptic children are in the planning process. The efficacy and safety data appear to be very promising considering the refractory nature of the epileptic population enrolled in studies to date. Results of ongoing phase III studies in adult epileptic patients are expected to be available in 2007 and are required to define the position of ESL in the therapy of patients with epilepsy.

Animals↗
PubMed2006

Dopamine D1-like receptor-mediated inhibition of Cl/HCO3- exchanger activity in rat intestinal epithelial IEC-6 cells is regulated by G protein-coupled receptor kinase 6 (GRK 6).

The present study investigated the effect of dopamine D1-like receptor stimulation on the Cl-/HCO3- exchange activity in rat intestinal epithelial IEC-6 cells. The Cl-/HCO3- exchange activity was found to be a chloride-dependent, DIDS-sensitive and niflumate-insensitive process. The presence of the SLC26A6 anion exchanger was detected by both RT-PCR and immunoblotting analysis in IEC-6 cells, in which three different small interfering RNAs (siRNAs) targeting SLC26A6 markedly inhibited Cl-/HCO3- exchange. Activation of dopamine D1-like receptors with SKF 38393 inhibited Cl-/HCO3- exchanger activity, this being antagonized by the D1 selective antagonist SKF 83566. However, effects of SKF 38393 were maximal at 5 min of exposure to the agonist and rapidly diminished with no effect at 15 min, suggestive of agonist-induced desensitization of D1-like receptors. Pretreatment of cells with heparin, a non-selective inhibitor of G protein-coupled receptor kinases (GRKs), prevented the observed attenuation of SKF 38393-induced inhibition of Cl-/HCO3- exchange. Overnight pretreatment with anti-GRK6A and anti-GRK6B, but not with anti-GRK4 antibodies, prevented the loss of SKF 38393-mediated effects. Both PKA and PKC signaling pathways participate in SKF 38393-mediated inhibition of Cl-/HCO3- exchange. These findings suggest that SLC26A6 is at least one of the anion exchanger's family members responsible for Cl-/HCO3- exchange in IEC-6 cells. Dopamine D1 receptors in IEC-6 rapidly desensitize to D1-like agonist stimulation and GRK 6, but not GRK 4, appear to be involved in agonist-mediated responsiveness and desensitization.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed2005

Synthesis and biological evaluation of a novel series of "ortho-nitrated" inhibitors of catechol-O-methyltransferase.

Novel regioisomeric "ortho-nitrated" catechols related to the catechol-O-methyltransferase (COMT) inhibitors BIA 3-202 3 and BIA 3-335 4 were synthesized and biologically evaluated. Changing the position of the nitro group from the "classical" meta- to the ortho-position relative to the side-chain substituent of the nitrocatechol pharmacophore exerted profound effects on selectivity and duration of COMT inhibition. Alkylaryl compounds 7a-d possessed shorter duration of action than their regioisomers, but 7b displayed reversed selectivity over 3 at 3 and 6 h, exhibiting preferential central inhibition. In the amino-substituted series, ortho-nitrated regioisomer 14k was less peripherally selective than 4 and short-acting, whereas decahydroquinoline 14g displayed an unprecedented combination of long-acting and selective peripheral inhibition. 7b could provide a useful tool to probe the pharmacological utility of short-acting, centrally selective COMT inhibitors in the treatment of depression in Parkinsonian patients, and 14g represents a promising candidate for clinical evaluation as an adjunct to L-Dopa therapy.

Animals↗
PubMed2005

Upregulation of apical NHE3 in renal OK cells overexpressing the rodent alpha(1)-subunit of the Na(+) pump.

Vectorial Na(+) reabsorption across the proximal tubule is mediated by apical entry of Na(+), primarily via Na(+)/H(+) exchanger isoform 3 (NHE3), and basolateral extrusion via the Na(+) pump (Na(+)-K(+)-ATPase). We hypothesized that regulation of Na(+) reabsorption should involve not only the activity of the basolateral Na(+)-K(+)-ATPase, but also the apical NHE3, in a concerted manner. To generate a cell line that overexpresses Na(+)-K(+)-ATPase, opossum kidney (OK) cells were transfected with the rodent Na(+)-K(+)-ATPase alpha(1)-subunit (pCMV ouabain vector), and native cells were used as a control. The existence of distinct functional classes of Na(+)-K(+)-ATPase in wild-type and transfected cells was confirmed by the inhibition profile of Na(+)-K(+)-ATPase activity by ouabain. In contrast to wild-type cells, transfected cells exhibited two IC(50) values for ouabain: the first value was similar to the IC(50) of control cells, and the second value was 2 log units greater than the first, consistent with the presence of rat and opossum alpha(1)-isozymes. It is shown that transfection of OK cells with Na(+)-K(+)-ATPase increased Na(+)-K(+)-ATPase and NHE3 activities. This was associated with overexpression of the Na(+)-K(+)-ATPase alpha(1)-subunit and NHE3 in transfected OK cells. The abundance of the Na(+)-K(+)-ATPase beta(1)-subunit was slightly lower in transfected OK cells. In conclusion, the increase in expression and function of Na(+)-K(+)-ATPase in cells transfected with the rodent Na(+) pump alpha(1)-subunit cDNA is expected to stimulate apical Na(+) influx into the cells, thereby accounting for the observed stimulation of the apical NHE3 activity.

Animals↗
PubMed2005

Interferon-gamma-induced STAT1-mediated membrane retention of NHE1 and associated proteins ezrin, radixin and moesin in HT-29 cells.

This study evaluated the effect of interferon-gamma (IFN-gamma) upon the function and expression of type 1 Na(+)/H+ exchanger (NHE1) in human intestinal epithelial HT-29 cells, namely that concerning the abundance of surface NHE1 and NHE1 binding to the ezrin, radixin and moesin (ERM) family of proteins. HT-29 cells express endogenous NHE1 and the ERM family of proteins that retain the localization of NHE1 in the membrane. Long-term exposure (24 h) of HT-29 cells to IFN-gamma resulted in a concentration-dependent decrease in NHE1 activity. Inhibition of NHE1 activity by IFN-gamma was absent after pretreatment with cariporide. The long-term exposure to IFN-gamma was accompanied by increase in surface NHE1 and ERM abundance and no changes in total NHE1 and ERM abundance. Inhibition of signal transducer and activator transcription factor 1 (STAT1) with epigallocatechin-3-gallate (EGCG) prevented the inhibitory effect of IFN-gamma. Treatment with IFN-gamma activated phospho-STAT1 was markedly attenuated by EGCG. The IFN-gamma-induced increase in surface NHE1 and ERM abundance was prevented by EGCG. In conclusion, long-term inhibition of NHE1 activity by IFN-gamma involves STAT1 phosphorylation and is accompanied by increased abundance of surface NHE1 and the NHE1 membrane anchoring ERM proteins.

Catechin↗
PubMed2005

Signaling of short- and long-term regulation of intestinal epithelial type 1 Na+/H+ exchanger by interferon-gamma.

The present study evaluated the effect of interferon-gamma (IFN-gamma) on intestinal Na+/H+ exchange (NHE) activity and the intracellular signaling pathways set into motion after IFN-gamma receptor activation. Caco-2 cells express endogenous NHE1, NHE2 and NHE3 proteins, as detected by immunoblotting. Short- (0.5 h) and long- (24 h) term exposure of Caco-2 cells to IFN-gamma resulted in a concentration-dependent decrease in NHE activity. Inhibition of NHE activity by IFN-gamma was absent in cariporide-treated cells, but not in cells treated with S-3226. The long-term exposure to IFN-gamma was accompanied by a 20% increase in surface NHE1 abundance and no changes in total NHE1 abundance. Inhibition of Raf1, mitogen-activated protein kinase kinase (MAPKK/MEK) and p38 MAPK with, respectively, GW 5074, PD 98059 and SB 203580 and downregulation of protein kinase C (PKC) with phorbol-12,13-dibutyrate (100 nM for 24 h) prevented inhibition of NHE activity by IFN-gamma (0.5 and 24 h exposure). The signal transducer and activator transcription factor 1 (STAT1) inhibitor epigallocatechin-3-gallate (EGCG) prevented inhibition of NHE activity by long- but not the short-term treatment with IFN-gamma. Treatment with IFN-gamma activated phospho-p38 MAPK, this effect being detected as early as 1 h, persisting over 3 h and decreasing after 24 h. IFN-gamma produced a sustained action of phospho-STAT1 that was prevented by EGCG and partially attenuated by SB 203580 and insensitive to downregulation of PKC. In conclusion, short- and long-term inhibition of NHE1 activity by IFN-gamma involves a complex signaling pathway that includes PKC activation and STAT1 phosphorylation, respectively, but is not accompanied by downregulation of NHE1.

Caco-2 Cells↗
PubMed2005

Effect of saline load and metoclopramide on the renal dopaminergic system in patients with heart failure and healthy controls.

Dopamine of renal origin has natriuretic/diuretic actions by activating D1-like receptors of the nephron. Saline load increases renal dopamine production and natriuresis in healthy subjects, and, under these conditions, the activation of D2-like receptors also produces natriuresis/diuresis. Metoclopramide is a D2-like receptor antagonist. Patients with heart failure (HF) have an increased renal dopamine-synthesizing efficiency. However, the effect of salt loading was not explored in HF. We hypothesized that HF patients respond to salt loading with increased production of renal dopamine and that metoclopramide antagonizes this response. This was a randomized, controlled, crossover study exploring the effect of NaCl and metoclopramide on renal dopaminergic, sympathetic, renin-angiotensin-aldosterone, and arginine-vasopressin (AVP) systems activity on sodium handling in 9 HF patients and 9 controls. NaCl markedly increased renal dopamine production and natriuresis in both groups. Metoclopramide blunted these responses in HF patients but not in controls. NaCl decreased renin and aldosterone plasma levels in controls but not in HF patients. In these patients B-type natriuretic peptide (BNP) levels increased, but AVP was not affected. HF patients respond to salt loading with increased natriuresis. However, the mechanisms for this response are different from those found in healthy subjects. Metoclopramide has antinatriuretic effects only in HF patients.

Aged↗
PubMed2005

Long-term effect of convulsive behavior on the density of adenosine A1 and A 2A receptors in the rat cerebral cortex.

PURPOSE: Adenosine is a neuromodulator that has been proposed to act as an anticonvulsant mainly via inhibitory A1 receptors, but recent data show that genetic deletion of facilitatory A 2A receptors might also attenuate convulsions. Since both A1 and A 2A receptors are prone to down- and upregulation in different stressful situations, we investigated if convulsive behavior leads to a long-term change in A1 and A 2A receptor density in the rat cerebral cortex. METHODS: Stage 4-5 convulsions (Racine's scale) were induced in adult Wistar rats either through amygdala stimulation (kindling) or by intraperitoneal injection of kainate (10 mg/ml). Rats were killed after 4 weeks to evaluate adenosine A1 and A 2A receptor density in the cerebral cortex using both Western blot and membrane binding assays. RESULTS: The binding density of the A1 antagonist, 3H-DPCPX, decreased by 40. +/- 4.4% and by 20.7 +/- 0.5% after kindling or kainate injection. Likewise, A1 receptor immunoreactivity in cortical membranes from kindled or kainate-injected rats decreased by 19.1 +/- 3.3% and 12.7 +/- 5.7%, respectively. In contrast, the binding density of the A 2A receptor antagonist 3H-SCH 58261 increased by 293 +/- 34% and by 159 +/- 32% in cortical membranes from kindled or kainate-injected rats, and A 2A receptor immunoreactivity also increased by 151 +/- 12% and 79.6 +/- 7.0%. CONCLUSIONS: This indicates that after convulsive behavior there is a long-term decrease of A1 receptors accompanied by an increased density of A 2A receptors, suggesting that A 2A antagonists rather than A1 agonists may be more promising anticonvulsive drugs.

Amygdala↗
PubMed2004

Synthesis, biological evaluation, and molecular modeling studies of a novel, peripherally selective inhibitor of catechol-O-methyltransferase.

A novel series of potent, peripherally selective, and long-acting inhibitors of catechol-O-methyltransferase (COMT) has been synthesized. The introduction and nature of heteroatom-containing substituents to the side-chain of the nitrocatechol pharmacophore was found to have a profound effect on both peripheral selectivity and duration of COMT inhibition in the mouse. This approach led to the discovery of 1-(3,4-dihydroxy-5-nitrophenyl)-3-[4-[3-(trifluoromethyl)phenyl]-1-piperazinyl]-1-propanone hydrochloride 35 (BIA 3-335), which was found to possess a superior inhibitory profile in vivo over both the nonselective inhibitor tolcapone 1 and the peripherally selective but short-acting entacapone 2. In this model, 35 retained 75% inhibition of peripheral COMT at 6 h after oral administration, yet significantly, only a minor reduction of central (cerebral) COMT activity was observed. Molecular modeling techniques were applied to review the analysis of the ternary enzyme-inhibitor complex previously determined by X-ray crystallography and to provide a deeper understanding of the structure-activity relationships within this novel series. Furthermore, a computational approach was applied in an effort to elucidate the particular structural factors relevant to the poor blood-brain permeability of 35. In conclusion, the improved biological properties herein reported reveal 35 as a candidate for clinical studies as an adjunct to L-DOPA therapy for Parkinson's disease.

Animals↗
PubMed2004

Intestinal Na+-K+-ATPase activity and molecular events downstream of interferon-gamma receptor stimulation.

This study evaluated the effects of human interferon-gamma (IFN-gamma) on Na(+)-K(+)-ATPase activity and the intracellular signaling pathways involved in human intestinal epithelial Caco-2 cells. Na(+)-K(+)-ATPase activity was determined as the difference between total and ouabain-sensitive ATPase. p38 MAP kinase activity was analyzed by Western blotting using the p38 MAP kinase assay kit. Total and phosphorylated STAT1 protein levels were detected using the PhosphoPlus Stat1. IFN-gamma decreased Na(+)-K(+)-ATPase activity in a time- and concentration-dependent manner. The IFN-gamma-induced decrease in Na(+)-K(+)-ATPase activity was accompanied by no changes in the abundance of alpha(1) subunit Na(+)-K(+)-ATPase. Downregulation of protein kinase C (PKC) with phorbol-12,13-dibutyrate (PDBu) prevented the inhibitory effect of IFN-gamma on Na(+)-K(+)-ATPase activity. Inhibition of Raf-1, mitogen-activated protein kinase kinase (MAPKK/MEK), p38 MAPK and STAT1 with, respectively, GW 5074, PD 98059, SB 203580 and epigallocatechin gallate prevented inhibition of Na(+)-K(+)-ATPase activity by IFN-gamma. Treatment with IFN-gamma markedly increased the expression of total and phospho-STAT1, this being accompanied by activation of p38 MAPK. Activation of phospho-STAT1 by IFN-gamma was almost abolished by epigallocatechin gallate and markedly reduced by SB 203580, but insensitive to downregulation of PKC. The increase in short circuit current (I(sc)) by 1.0 and 2.5 micrograms ml(-1) amphotericin B was markedly attenuated in IFN-gamma-treated cells. However, the inhibitory effect of PDBu on the amphotericin B-induced increase in I(sc) was of similar magnitude in vehicle- and IFN-gamma-treated cells. It is concluded that IFN-gamma markedly attenuates Na(+)-K(+)-ATPase activity. The transduction mechanisms set into motion by IFN-gamma involve the activation of PKC downstream STAT1 phosphorylation and Raf-1, MEK, ERK2 and p38 MAPK pathways, in a complex sequence of events.

Caco-2 Cells↗
PubMed2004

Dopamine D3 receptor-mediated inhibition of Na+/H+ exchanger activity in normotensive and spontaneously hypertensive rat proximal tubular epithelial cells.

This study evaluated the response of the Na(+)/H(+) exchanger (NHE) to dopamine D(1)- and D(2)-like receptor stimulation in immortalized renal proximal tubular epithelial cells and freshly isolated renal proximal tubules from the spontaneously hypertensive rat (SHR) and their normotensive controls (Wistar Kyoto rats; WKY). Stimulation of D(1)-like receptors with SKF 38393 attenuated NHE activity in WKY cells (IC(50)=151 nM), but not in SHR cells. Stimulation of D(2)-like receptors with quinerolane (IC(50)=120 nM) attenuated NHE activity in SHR cells, but not in WKY cells. Forskolin was equipotent in SHR and WKY cells in inhibiting NHE activity. The effect of SKF 38393 was abolished by overnight treatment of WKY cells with cholera toxin (CTX, 500 ng ml(-1)), but not with pertussis toxin (PTX, 100 ng ml(-1)). The effect of quinerolane (1 microm) was abolished by overnight treatment of SHR cells with PTX, but not with CTX. The D(3) receptor agonist 7-OH-DPAT (IC(50)=0.8 microM) attenuated NHE activity in SHR cells only. This effect was abolished by S-sulpiride and by overnight treatment with PTX. The D(4) receptor agonist RBI 257 did not affect NHE activity. The 7-OH-DPAT inhibited NHE activity in freshly isolated renal proximal tubules from 4- and 12-week-old SHR and 12-week-old WKY, but not in freshly isolated renal proximal tubules from 4-week-old WKY. It is concluded that D(3) receptors coupled to a G(i/o) protein play a role in the handling of tubular Na(+), namely through inhibition of the NHE activity, this being of particular relevance in the SHR, which fail to respond to D(1)-like dopamine receptor stimulation.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed2004

Gialpha3 protein-coupled dopamine D3 receptor-mediated inhibition of renal NHE3 activity in SHR proximal tubular cells is a PLC-PKC-mediated event.

This study evaluated the transduction pathway associated with type 3 Na(+)/H(+) exchanger (NHE3) activity-induced inhibition during dopamine D(3) receptor activation in immortalized renal proximal tubular epithelial cells from the spontaneously hypertensive rat. The dopamine D(3) receptor agonist 7-OH-DPAT decreased NHE3 activity, which was prevented by the D(2)-like receptor antagonist S-sulpiride, pertussis toxin (PTX; overnight treatment), and the PKC inhibitor chelerythrine, but not by cholera toxin (overnight treatment), the MAPK inhibitor PD-098059, or the p38 inhibitor SB-203580. The PKA inhibitor H-89 abolished the inhibitory effects of forskolin on NHE3 activity, but not that of 7-OH-DPAT. The phospholipase C (PLC) inhibitor U-73122 prevented the inhibitory effects of 7-OH-DPAT, whereas PDBu and 7-OH-DPAT increased PLC activity and reduced NHE3 activity; downregulation of PKC abolished the inhibitory effects of both PDBu and 7-OH-DPAT on NHE activity. The inhibition of NHE3 activity by GTPgammaS and the prevention of the effect of 7-OH-DPAT by PTX suggest an involvement of a G(i/o) protein coupled to the dopamine D(3) receptor. Indeed, the 7-OH-DPAT-induced decrease in NHE3 activity was abolished in cells treated overnight with the anti-G(i)alpha3 antibody, but not in cells treated with antibodies against G(q/11), G(s)alpha, G(beta), and G(i)alpha1,2 proteins. The calcium ionophore A-23187 and the Ca(2+)-ATPase inhibitor thapsigargin increased intracellular Ca(2+) but did not affect NHE3 activity. However, the inhibitory effects of PDBu and 7-OH-DPAT on NHE3 activity were completely abolished by A-23287 and thapsigargin. It is concluded that inhibition of NHE3 activity by dopamine D(3) receptors coupled to G(i)alpha3 proteins is a PLC-PKC-mediated event, modulated by intracellular Ca(2+).

Animals↗
PubMed2004

Involvement of G protein-coupled receptor kinase 4 and 6 in rapid desensitization of dopamine D1 receptor in rat IEC-6 intestinal epithelial cells.

Dopamine-induced inhibition of Na(+)-K(+)-ATPase has been suggested to play a role in the regulation of Na(+) absorption at the intestinal level, and these effects were mediated by dopamine D(1)-like receptors. The aim of this work was to evaluate the effect of the activation of the D(1)-like receptors on the activity of the Na(+)/H(+) exchanger (NHE) in the rat intestinal epithelial cell line IEC-6. The presence of D(1) receptors was confirmed by immunoblotting. The dopamine D(1)-like receptor agonist SKF-38393 produced a concentration-dependent inhibition of NHE activity and stimulation of adenylyl cyclase (AC), this being antagonized by the D(1) selective antagonist SKF-83566. Effects of SKF-38393 on NHE and AC activities were maximal at 5 min of exposure to the agonist and rapidly diminished with no effect at 25 min. Exposure of cells for 25 min to dibutyryl-cAMP (0.5 mM) or to the AC activator forskolin (3 microM) effectively inhibited NHE activity. Pretreatment of cells with heparin (1 microM), a nonselective G protein-coupled receptor kinase (GRK) inhibitor, prevented the loss of effects on NHE activity after 25 min exposure to SKF-38393. The presence of GRK4, GRK6A, and GRK6B was confirmed by immunoblotting. Overnight treatment with the anti-GRK4-6 antibody complexed with Lipofectin was also effective in preventing loss of the effects of SKF-38393 on NHE and AC activities. It is concluded that dopamine D(1) receptors in IEC-6 rapidly desensitize to D(1)-like agonist stimulation and GRK4 and 6 appear to be involved in agonist-mediated responsiveness and desensitization.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed2004

Dopamine acutely decreases type 3 Na(+)/H(+) exchanger activity in renal OK cells through the activation of protein kinases A and C signalling cascades.

Dopamine D(1)-mediated inhibition of Na(+),K(+)-ATPase activity in opossum kidney (OK) cells involves the sequential activation of the adenylyl cyclase-protein kinase A (PKA) and the phospholipase C-protein kinase C (PKC) pathways. The present study evaluated the signalling cascades involved in dopamine-mediated inhibition of Na(+)/H(+) exchanger isoform 3 (NHE3) in OK cells. The transport kinetics displayed a simple Michaelis-Menten relationship for extracellular Na(+) of 25+/-6 mM. Dopamine and the dopamine D(1)-like receptor agonist SKF 38393 ((+/-)-1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzazepine-7,8-diol) inhibited NHE3 activity in a concentration-dependent manner; the dopamine D(2)-like receptor agonist quinerolane was devoid of effect. The SKF 38393-mediated inhibition of NHE3 was prevented either by the dopamine D(1)-like receptor antagonist SKF 83566 ((+/-)-7-Bromo-8-8-hydroxy-3 methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine; 1 microM), overnight treatment with cholera toxin (500 ng/ml), the PKA antagonist H-89 (N-(2-[p-bromocinnamylamino]ethyl)-5 isoquinolinesulfonamide hydrochloride; 10 microM), the PKC antagonist chelerythrine (1 microM), or the phospholipase C inhibitor U-73,122 (1-(6-[(17beta]-3-methoxyestra-1,3,5[10]-trien-17-yl) amino] hexyl)-1H-pyrrole-2,5-dione; 3 microM). In addition, dibutyril cAMP (dB-cAMP; 500 microM) was found to increase phospholipase C activity, both in membranes and in cytosol from OK cells; in contrast, phorbol-12,13-dibutyrate (PDB) (1 microM) did not have a significant effect on phospholipase C activity. Pre-treatment of OK cells with the anti-G(s)alpha antibody, but not the anti-G(q/11)alpha antibody, blunted the inhibitory effect of SKF 38393 on NHE3 activity. It is concluded that dopamine D(1)-mediated inhibition of NHE3 in renal OK cells involves both adenylyl cyclase-PKA and the phospholipase C-PKC pathways, a mechanism similar to that described for Na(+),K(+)-ATPase.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed2004

Renal dopamine and salt sensitivity of blood pressure in IgA nephropathy.

BACKGROUND: Patients with chronic glomerulonephritis exhibit salt-sensitive (SS) hypertension. In the early stage, however, the exact characteristics are still unclear. A decrease in renal dopamine production under basal conditions or after a sodium load has been reported in a subset of patients with SS primary hypertension. AIMS: The present study examined 17 untreated IgA-N patients with near-normal renal function, to determine whether salt sensitivity appears before hypertension and whether this sensitivity is related to renal dopamine production. METHODS: Daily urinary excretion of dopamine, the amine precursor--L-DOPA, and metabolites was monitored in conditions of basal sodium ingestion, followed by three consecutive 5-day periods of 100, 20 and 350 mmol/day sodium intake. The sodium sensitivity index (SSI) was evaluated in each patient. In addition, the patients were considered SS when showing an increase > or =5 mm Hg in 24-hour mean BP when they changed from a 20- to a 350-mmol/day sodium diet. RESULTS: Urinary dopamine output was lower in SS than in salt-resistant patients throughout the study (p < 0.001). This was accompanied by lower creatinine clearance values and higher urinary protein excretion in SS IgA-N patients. A strong negative relationship was observed in these 17 IgA-N patients between the SSI and the daily urinary excretion of dopamine in conditions of both 20 mmol/day sodium intake (r2 = 0.592; p = 0.0003) and 350 mmol/day sodium diet (r2 = 0.352; p = 0.01). However, urinary dopamine output varied appropriately throughout the study in SS patients, in agreement with changes in sodium intake. CONCLUSION: We conclude that in IgA-N patients, a rightward shift in the 'pressure natriuresis' can appear before hypertension and is related with a reduced renal production of dopamine. It is suggested that decreased renal dopamine synthesis in SS IgA-N patients results from acquired tubulointerstitial injury. In contrast to what has been found in SS primary hypertension, renal dopamine may behave appropriately in SS IgA-N patients, as a compensatory hormone.

Adult↗
PubMed2004

Neurotoxicity induced by antiepileptic drugs in cultured hippocampal neurons: a comparative study between carbamazepine, oxcarbazepine, and two new putative antiepileptic drugs, BIA 2-024 and BIA 2-093.

PURPOSE: Newly designed antiepileptic drugs (AEDs) are being evaluated for their efficacy in preventing seizures and for their toxic profiles. We investigated and compared the toxic effects of two dibenz[b,f]azepine derivatives with anticonvulsant activity, 10,11-dihydro-10-hydroxyimino-5H-dibenz[b,f]azepine-5-carboxamide (BIA2-024) and (S)-(-)-10-acetoxy-10,11-dihydro-5H-dibenz[b,f] azepine-5-carboxamide (BIA2-093), with the structurally related compounds carbamazepine (CBZ) and oxcarbazepine (OXC), both in current use for the treatment of epilepsy. METHODS: Primary rat hippocampal neurons were used to evaluate neuronal morphology and biochemical changes induced by the AEDs used in this study. Immunocytochemical staining against MAP-2 was used to evaluate neuronal morphology. Reactive oxygen species (ROS) and changes in mitochondrial membrane potential (Psim) were measured by fluorescence techniques. Intracellular adenosine triphosphate (ATP) levels were quantified by high-performance liquid chromatography (HPLC). RESULTS: Hippocampal neurons treated for 24 h with CBZ or OXC (300 microM) showed degeneration and swelling of neurites, but this effect was not observed in neurons treated with BIA 2-024 or BIA 2-093 (300 microM). ROS production also was increased in neurons treated with OXC, but not in neurons treated with the other AEDs. ATP levels were significantly decreased only in neurons treated with OXC, although the energy charge was not altered. Furthermore, OXC led to a decrease of Psim. CONCLUSIONS: In all parameters assayed, OXC was more toxic than the other AEDs used. Because the new putative AEDs have previously been shown to have an efficacy in preventing seizures similar to that of CBZ and OXC, and are less toxic to neuronal cells, they may be considered as alternatives to the current available therapies for the treatment of epilepsy.

Animals↗
PubMed2004

High- and low-affinity transport of L-leucine and L-DOPA by the hetero amino acid exchangers LAT1 and LAT2 in LLC-PK1 renal cells.

The present study examined the functional characteristics of the inward and outward L-[14C]DOPA and L-[14C]leucine transporters in LLC-PK1 cells. Uptake was initiated by the addition of Hanks' medium with a given concentration of L-[14C]DOPA or L-[14C]leucine. Saturation experiments were performed in cells incubated for 6 min with 0.25 microM concentration of the substrates in the absence and the presence of increasing concentrations of the nonlabeled substrates. Fractional outflow of intracellular L-[14C]DOPA or L-[14C]leucine was evaluated in cells loaded with 2.5 microM L-[14C]DOPA or 1 microM L-[14C]leucine for 6 min and then the corresponding efflux was monitored over 24 min. The high-affinity (Km = 5.1 microM) uptake of L-[14C]leucine and the low-affinity (Km = 120.0 microM) uptake of L-[14C]DOPA were largely promoted through a Na+-independent transporter. The uptake of the substrates was insensitive to N-(methylamino)-isobutyric acid but competitively inhibited by 2-aminobicyclo(2,2,1)-heptane-2-carboxylic acid (BCH). L- And D-neutral amino acids, but not acidic and basic amino acids, markedly inhibited L-[14C]DOPA and L-[14C]leucine accumulation. The uptake of L-[14C]leucine was a pH-insensitive process, whereas that of L-[14C]DOPA was sensitive to pH. The efflux of L-[14C]DOPA and L-[14C]leucine was markedly increased (P < 0.05) by L-cysteine, L-leucine, BCH, and L-DOPA but not by L-arginine. RT-PCR detected LAT1 and LAT2 transcripts in LLC-PK1 cells. It is concluded that LLC-PK1 cells express both LAT1 and LAT2 transcripts and transport L-[14C]leucine through the Na+-independent pH-insensitive and high-affinity LAT1 transporter, whereas L-[14C]DOPA is mainly transported through the Na+-independent pH-insensitive and low-affinity LAT2 transporter and a minor component through a Na+-dependent transporter.

Animals↗