Biomedical subjects

R P Garay

Publications and source records attributed to R P Garay.

At least 19 recordsLinked to original sources

PubMed2004

Inhibition by reproterol of cAMP PDE in intact mastocytoma P-815 cells.

In vitro studies in rat mastocytes and human monocytes suggested that reproterol (a selective beta(2)-adrenoceptor agonist with a theophylline moiety) exerts anti-inflammatory actions through inhibition of cyclic AMP (cAMP) PDE activity. Thus, reproterol was tested for its ability to inhibit cAMP PDE in cultured mouse mastocytoma P-815 cells. cAMP PDE activity was measured in intact cells by spectrofluorometry using the fluorescent substrate 2'-O-anthraniloyl cAMP. Reproterol was more potent than theophylline to inhibit cAMP PDE (pIC(50)=4.28+/-0.25 vs. 3.16+/-0.05). This contrasted with disrupted cells, where the PDE inhibitory potency of reproterol was low (pIC(50)=2.85+/-0.03) and similar to that of theophylline (pIC(50)=2.66+/-0.19). No cAMP PDE inhibition was found with other beta(2)-agonists tested (fenoterol, salbutamol, salmeterol and formoterol). Finally, the selective PDE inhibitors calmidazolium (100 nM), milrinone (5 microM) and rolipram (50 microM) inhibited cAMP PDE activity by approximately 20, 30 and 25% respectively. In conclusion, reproterol potently and non-specifically inhibited intracellular cAMP phosphodiesterases in intact mastocytoma cells. This can explain the previously reported beta(2)-adrenoceptor-independent anti-inflammatory actions of reproterol in vitro. Further studies are required to define the anti-inflammatory potential of reproterol in asthma.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2003

Reduction of extracellular dopamine and metabolite concentrations in rat striatum by low doses of acute cyamemazine.

The low incidence of extrapyramidal effects with atypical neuroleptics has been ascribed to their 5-HT(2A)- and 5-HT(2C)-serotonin receptor antagonistic properties. On the other hand, the acute increase in striatal dopamine release by submaximal dopamine D(2) autoreceptor blockade can be respectively reduced and increased by 5-HT(2A)- and 5-HT(2C)-antagonists. Cyamemazine is a neuroleptic D(2)- and 5-HT(2A)-receptor antagonist, with small antagonistic activity at 5-HT(2C) receptors and low incidence of extrapyramidal side effects. Therefore, submaximal cyamemazine was tested in rats for its acute action on the extracellular concentrations of dopamine and dopamine metabolites (DOPAC: 3,4,dihydroxyphenylacetic acid and HVA: 4-hydroxy-3-methoxy-phenyl-acetic acid) in the corpus striatum. The serotonin metabolite 5-HIAA (5-hydroxy-indole-acetic acid) was measured in parallel. Rats prepared for microdialysis (striatum) were intraperitoneally given cyamemazine 1 mg/kg, 5 mg/kg or vehicle ( n=4 in each group). Dopamine, DOPAC, HVA and 5-HIAA concentrations in perfusates under basal conditions and after stimulation by high K(+) were measured by HPLC coupled to electrochemical detection. Cyamemazine 1 mg/kg significantly reduced extracellular concentrations of basal dopamine (-77%), DOPAC (-54%), HVA (-54%) and 5-HIAA (-65%). No such effects were seen with the dose of cyamemazine 5 mg/kg or for K(+)-evoked dopamine release. In conclusion, submaximal cyamemazine can acutely reduce basal dopamine release and metabolism in the rat striatum. Such unusual action can be explained by the original pharmacological profile of cyamemazine (potent D(2)- and 5-HT(2A)-antagonist, with small antagonistic activity at 5-HT(2C) receptors). Further experiments are required to explain the low incidence of extrapyramidal side actions with cyamemazine.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2002

Rat NKCC2/NKCC1 cotransporter selectivity for loop diuretic drugs.

It is generally assumed that bumetanide possesses some selectivity for the renal Na-K-Cl cotransporter NKCC2, although the results are scarce in the literature and comparisons were done with extra-renal NKCC1 at its basal, almost silent state. Here we investigated NKCC2/NKCC1 selectivity of loop diuretic drugs (bumetanide, piretanide and furosemide) as a function of the NKCC1 activated state (NKCC1 was activated by hypertonic media). NKCC2 activity was measured in isolated rat medullary thick ascending limb (mTAL) and NKCC1 in rat thymocytes and erythrocytes. When NKCC2 was compared with NKCC1at its activated state, all three diuretic drugs inhibited NKCC2 and NKCC1 with the same potency (bumetanide pIC50=6.48, 6.48 and 6.47; piretanide pIC50=5.97, 5.99 and 6.29; and furosemide pIC50=5.15, 5.04 and 5.21 for mTAL NKCC2, erythrocyte NKCC1 and thymocyte NKCC1, respectively). Basal NKCC1 exhibited a lower diuretic sensitivity, although with marked differences depending on the diuretic drug and the cell type in consideration and with the notable exception of furosemide in erythrocytes. Molecular modelling showed that bumetanide and piretanide possess four potentially active groups, of which three are shared with furosemide at similar intergroup distances. Of these three common groups, one should not bind to basal NKCC1 in thymocytes. The fourth (phenoxy) group (absent in furosemide) confers higher lipophilicity and should not bind to basal NKCC1 in erythrocytes. In conclusion, loop diuretics had no NKCC2/NKCC1 selectivity, when NKCC1 is measured at its activated state. Basal NKCC1 has a reduced diuretic sensitivity, of very different magnitude depending on the diuretic drug and cell type in consideration.

Animals↗

PubMed2001

Antioxidant properties of calcium dobesilate in ischemic/reperfused diabetic rat retina.

Calcium dobesilate possesses antioxidant properties and protects against capillary permeability by reactive oxygen species in the rat peritoneal cavity, but whether a similar action can take place in the diabetic rat retina is unknown. We investigated the oral treatment of diabetic rats with calcium dobesilate on the prevention of free radical-mediated retinal injury induced by ischemia/reperfusion (90 min ischemia followed by 3 min and/or 24 h of reperfusion). Streptozotocin-induced diabetic rats were orally treated with 50 and 100 mg/kg of calcium dobesilate for 10 days (n=12 in each group). In the first series of studies, calcium dobesilate was found to significantly reduce the maldistribution of ion content in diabetic ischemic/reperfused rat retina. Thus, in diabetic rats treated with 100 mg/kg/day calcium dobesilate, ischemia/reperfusion provoked: (i) 27.5% increase in retinal Na(+) content compared to 51.8% in the vehicle-treated group (P<0.05), and (ii) 59.6% increase in retinal Ca(2+) content compared to 107.1% in vehicle-treated animals (P<0.05). In the second series of studies, calcium dobesilate was found to significantly protect diabetic rat retina against inhibition of Na(+)/K(+)-ATPase and Ca(2+)/Mg(2+)-ATPase activities by ischemia/reperfusion (54% and 41% reduction, respectively, with 100 mg/kg of calcium dobesilate) and also against changes in retinal ATP, reduced glutathione (GSH), and oxidized glutathione (GSSG) contents. In the third series of experiments, rats treated with 100 mg/kg of calcium dobesilate reduced the hydroxyl radical signal intensity to 41% (measured by electron paramagnetic resonance), induced by ischemia/reperfusion in diabetic rat retina. Finally, 100 mg/kg calcium dobesilate significantly reduced retinal edema (measured by the thickness of the inner plexiform layer) in diabetic rats. In conclusion, oral treatment with calcium dobesilate significantly protected diabetic rat retina against oxidative stress induced by ischemia/reperfusion. Whether the antioxidant properties of calcium dobesilate explain, at least in part, its beneficial therapeutic effects in diabetic retinopathy deserves further investigation.

Adenosine Triphosphate↗

PubMed2000

Dramatic magnesium efflux induced by high potassium in rat thymocytes.

When incubated in 150 mM KCl, rat thymocytes exhibited a very important magnesium efflux (11.4 +/- 0.7 mmoles/liter cells/20 min, n = 29), about 90 times higher than the physiological magnesium efflux catalyzed by the Na-Mg exchanger (0.126 +/- 0.093 mmoles/liter cells/20 min). Cells remained viable (trypan blue test) and membrane integrity was shown by the absence of an increase in sodium permeability. K(+)-induced magnesium efflux exhibited the following properties: (i) it required the presence of external chloride; (ii) it was fully blocked by DIOA, a selective KCl-cotransporter inhibitor (IC(50) = 35 microm); and (iii) it was associated to a progressive increase in cell volume via the DIOA-sensitive K-Cl cotransporter. Such cell swelling seems to play a causal role, because (i) hypertonic media (+400 mM sucrose) abolished K(+)-induced magnesium efflux and (ii) hypotonic Ringer media (205 mOsm) increased both cell volume and magnesium efflux (from a basal value of 0.35 +/- 0.03 mmoles/liter cells/20 min up to 1.44 +/- 0.24 mmoles/liter cells/20 min), even in the presence of DIOA. In conclusion, high potassium induced a dramatic release of intracellular magnesium from rat thymocytes. Such a phenomenon was, at least in part, caused by cell swelling via the DIOA-sensitive K-Cl cotransporter. The nature of the magnesium transport mechanism and its role in the transduction signal of K-Cl cotransporter activation by cell swelling deserve further investigation.

Animals↗

PubMed2000

5-HT3- and 5-HT2C-antagonist properties of cyamemazine: significance for its clinical anxiolytic activity.

RATIONALE: Cyamemazine is a neuroleptic compound which possesses anxiolytic properties in humans. On the other hand, 5-HT3- and 5-HT2C-receptors have been implicated in anxiety disorders and a previous binding study has shown that cyamemazine possesses high affinity for both serotonin receptor types. OBJECTIVE: The present study was undertaken to establish whether cyamemazine antagonizes 5-HT3- and/or 5-HT2C-mediated responses, and whether it compares with reference compounds. METHODS: Cyamemazine was tested for its ability to antagonize: (i) 5-HT3-dependent contraction of the isolated guinea-pig ileum and bradycardic responses in the rat and (ii) 5-HT2C-dependent phospholipase C (PLC) stimulation in rat brain membranes. RESULTS: In isolated guinea-pig ileum, cyamemazine potently and competitively antagonized 5-HT-dependent contractions (pA2 = 7.52 +/- 0.08; n = 5). In this test, cyamemazine was 5-7 times more potent (pIC50 = 6.75 +/- 0.13) than tropisetron (pIC50 = 6.02 +/- 0.04). In rats, cyamemazine i.v. antagonized 5-HT-dependent bradycardic responses with ID50% = 3.2 +/- 1.5 mg/kg (n = 4). Finally, in rat brain membranes cyamemazine antagonized 5-HT2C-dependent PLC stimulation with Ki = 424 nM (mianserin exhibits a Ki = 113 nM). CONCLUSIONS: Cyamemazine behaves as an antagonist at both 5-HT3- and 5-HT2C-receptors, which compares well with reference compounds. These 5-HT3- and 5-HT2C-antagonistic actions of cyamemazine can be involved, at least in part, in its beneficial therapeutic actions in anxiety disorders.

Animals↗

PubMed2000

[Cellular mechanisms of smooth muscle contraction].

Myosin is an ATPase, able to form filaments with actin, thus initiating smooth muscle contraction (conversion of chemical energy into mechanical energy). Myosin activity is regulated by cytosolic calcium, via a calcium-calmodulin-MLCK-dependent phosphorylation. Extrusion of cytosolic calcium via calcium pumps (in the plasma membrane and sarcoplasmic reticulum) and via a sodium-calcium exchange allow smooth muscle cells to maintain their resting state. Constrictor agonists (hormones, neurotransmitters or drugs) act at membrane receptors inducing: (i) a fast and transient calcium mobilization from the sarcoplasmic reticulum, via phospholipase C (PLC) stimulation and inositol triphosphate (IP3) production or via a "calcium-induced calcium release" mechanism and opening of calcium channels in the sarcoplasmic reticulum and (ii) a slow and maintained mobilization of extracellular calcium, via the opening of voltage-dependent calcium channels in plasma membranes. Smooth muscle relaxation is ensured by a phosphatase which hydrolyzes phosphorylated myosin and decreases the calcium sensitivity of the contractile apparatus. Calcium signal is regulated at that level by: (i) protein kinase C, tyrosine kinase and arachidonic acid which inhibit phosphatase activity and (ii) cyclic AMP (cAMP) and cyclic GMP (cGMP) which enhance phosphatase activity. A second regulatory site is situated at the level of the non-contractile calcium compartment, which buffers signal transduction and where cGMP and/or cAMP enhance calcium extrusion mechanisms.

Calcium Signaling↗

PubMed1999

Enhancement by reproterol of the ability of disodium cromoglycate to stabilize rat mastocytes.

The beta2-adrenoceptor agonist reproterol and disodium cromoglycate (DSCG) are used in fixed combination for the treatment of asthma, because they act on bronchial smooth muscle and inflammatory cells, respectively. Here, we investigated if reproterol can also act in rat mast cells in vitro to facilitate the inhibitory action of disodium cromoglycate (DSCG) on histamine secretion induced by compound 48/80. Reproterol was as potent as DSCG to inhibit histamine release in rat mast cells (32.8+/-6.0 vs. 36.7+/-6.2% at 1 microM of each compound, n=10 and n=8 respectively). Mast cell stabilization by DSCG (1-100 microM) was strongly and significantly enhanced in the presence of a fixed saturating concentration of reproterol (100 microM). Conversely, the combination of DSCG (1-100 microM) with the beta2-agonist used as reference compound, salbutamol (100 microM) did not inhibit histamine release more than DSCG alone. In combination with a saturating concentration of DSCG (100 microM), reproterol inhibited histamine release more than reproterol alone. The potent adenylate cyclase stimulator forskolin (50 microM) was able to inhibit histamine release to a similar extent as DSCG and significantly (P<0.05) enhanced the inhibition of histamine release by DSCG. Finally, the phosphodiesterase inhibitor theophylline (100 microM) was equipotent to reproterol and DSCG in stabilizing rat mast cells. In conclusion, reproterol enhances the ability of disodium cromoglycate to stabilize rat mast cells. This effect is not shared by salbutamol and can be, at least in part, independent of beta2-adrenoceptor stimulation.

Adrenergic beta-Agonists↗

PubMed1999

Selective blockade by nicergoline of vascular responses elicited by stimulation of alpha 1A-adrenoceptor subtype in the rat.

The alpha 1-adrenergic blocking activity of nicergoline was re-examined in rats, with a particular emphasis on alpha 1-adrenoceptor subtypes. In pithed rats, nicergoline and prazosin infused at a single small dose (0.5 microgram/kg/min i.v.) produced a substantial and identical shift to the right of the control dose pressor response curve to the specific alpha 1-agonist cirazoline (ED50 = 4.0 +/- 0.1, 4.0 +/- 0.1 and 0.9 +/- 0.01 microgram/kg i.v. for nicergoline, prazosin and vehicle respectively). In the isolated perfused mesenteric vascular bed, nicergoline strongly inhibited the pressor responses elicited by cirazoline, with approximately 40-fold higher potency (pA2 = 11.1 +/- 0.3) than prazosin (pA2 = 9.5 +/- 0.3). Conversely, nicergoline was 20-fold less potent than prazosin to antagonize the contractile effects of cirazoline in isolated endothelium-denuded aorta (pA2 = 8.6 +/- 0.2 and 9.9 +/- 0.2 for nicergoline and prazosin respectively). Pretreatment of mesenteric vascular beds with chloroethylclonidine did not significantly modify nicergoline antagonistic potency (pA2 = 10.6 +/- 0.2). Nicergoline displaced [3H]-prazosin bound to rat forebrain membranes pretreated with chloroethylclonidine (pKi = 9.9 +/- 0.2) at concentrations 60-fold lower than in rat liver membranes (pKi = 8.1 +/- 0.2). Finally, of the nicergoline metabolites studied, lumilysergol acted as a modest alpha 1 antagonist (bromonicotinic acid was devoid of alpha 1 antagonist activity). In conclusion, nicergoline is a potent and selective alpha 1A-adrenoceptor subtype antagonist, an alpha 1-adrenoceptor subtype which is mainly represented in resistance arteries.

Adrenergic alpha-1 Receptor Antagonists↗

PubMed1999

[Lack of effect of cicletanine and its sulfoconjugated metabolite on the thiazide receptor expressed in Xenopus oocytes].

UNLABELLED: Although the renal receptor at which cicletanine acts is unknown, cicletanine was assumed to act like thiazide diuretics. Here we tested cicletanine and its natriuretic metabolite, cicletanine-sulfate, for inhibitory activity against the thiazide-sensitive NaCl cotransporter expressed in Xenopus oocytes. The renal thiazide-sensitive NaCl cotransporter was expressed in Xenopus laevis oocytes injected with rat cRNA TSCr (TSCr: thiazide-sensitive cotransporter from rat kidney) and both, racemic (+/-) cicletanine and its sulfoconjugated metabolite were tested for inhibitory activity against oocyte 22Na+ uptake catalyzed by this cotransporter. Polythiazide was used as reference thiazide. Polythiazide fully inhibited NaCl cotransporter function with IC50 approximately 1.2 x 10(-7) M. Conversely, neither cicletanine, nor cicletanine sulfate were able to inhibit such cotransporter, i.e.: a minimum concentration of 10(-4) M of cicletanine was necessary to induce a slight cotransporter inhibition (29.5 +/- 18.2%). Cicletanine sulfate was inactive, even at 10(-4) M. IN CONCLUSION: (i) the natriuretic metabolite of cicletanine (cicletanine sulfate) is unable to inhibit thiazide-sensitive NaCl cotransporter and (ii) inhibition of such cotransporter by cicletanine required concentrations equal or higher than 10(-4) M--concentrations much more higher than urinary therapeutic ones in humans (approximately 10(-6) M). These results clearly demonstrate that cicletanine does not act like thiazide diuretics.

Animals↗

PubMed1999

[Na-K-Cl cotransporters and "salt-sensitive" arterial hypertension].

In the 80s, erythrocyte Na-K-Cl cotransporter of essential hypertensive was reported: (i) decreased in fresh erythrocytes and (ii) increased, following repeated cell washings and incubations. This suggested to us that the manipulation of erythrocytes (from essential hypertensives) was able to dissociate a cotransport inhibitory factor, thus unmasking up-regulation of membrane cotransport units. This working hypothesis was recently confirmed in Dahl salt-sensitive rats (DS). The primary defect of DS rats seems to be hyperactivity of cotransporter Na-K-Cl BSC1 at the thick ascending limb of Henle's loop (TAL). Moreover, oral salt-loading induces an abnormally high increase in the urinary and plasmatic CIF levels of DS rats. The increase in urinary CIF excretion seems to be a compensatory mechanism, able to reduce BSC1 hyperactivity and NaCl reabsorption at the TAL. The increase in plasmatic CIF should inhibit erythrocyte BSC2, thus inducing "up-regulation" of the membrane density of cotransport proteins. Further studies are required to test this model in human with "salt-sensitive" hypertension.

Absorption↗

PubMed1998

Angioprotective action of calcium dobesilate against reactive oxygen species-induced capillary permeability in the rat.

Calcium dobesilate possesses antioxidant properties in vitro, but the in vivo significance and putative angioprotective role of these properties are undefined. Here, calcium dobesilate was tested in a newly developed in vivo model of microvascular permeabilization induced by reactive oxygen species in the rat peritoneal cavity. In this model, microvascular permeabilization is equated to the rate of Evans blue extravasation toward the peritoneal cavity. Basal Evans blue extravasation (rate constant values ke = 0.0176 +/- 0.0015 h-1) was markedly and significantly increased by reactive oxygen species generated in situ, with: (i) phenazine methosulfate/NADH (delta ke(phenazine methosulfate) = 0.0419 +/- 0.0043 h-1) and (ii) xanthine/xanthine oxidase (delta ke(xo) = 0.0383 +/- 0.0010x h-1). These actions of reactive oxygen species were abolished by locally injected superoxide dismutase (i.p., 300 units/kg). Intraperitoneally given calcium dobesilate (100 mg/kg) inhibited 75-100% of reactive oxygen species-induced Evans blue extravasation. By the intravenous route, calcium dobesilate i.v. (1-50 mg/kg) dose dependently inhibited phenazine methosulfate-induced Evans blue extravasation with an ID50 of 2-5 mg/kg (full inhibition was reached at 20-50 mg/kg). After single oral administration, calcium dobesilate (5-500 mg/kg) dose dependently inhibited phenazine methosulfate-dependent Evans blue extravasation with an ID50 of 50-100 mg/kg (81% inhibition at 500 mg/kg, P < 0.003). After 7 days of oral calcium dobesilate (50 mg/kg once/day) phenazine methosulfate-induced Evans blue peritoneal extravasation was significantly reduced by half. These effects of calcium dobesilate were similar to those observed with a comparative antioxidant molecule, rutin. In conclusion, rat peritoneal microvascular permeability was strongly increased by reactive oxygen species, an effect that was significantly reduced by intraperitoneal, intravenous and oral calcium dobesilate. These results support the hypothesis that the antioxidant properties of calcium dobesilate could play a role in its angioprotective properties in vivo.

Administration, Oral↗

PubMed1998

Inhibition by (-)-cicletanine of the vascular reactivity to angiotensin II and vasopressin in isolated rat vessels.

In pithed rats, the levorotatory (-)-enantiomer of cicletanine reduces the pressor responses to angiotensin II (AII) and also, to a lesser extent, those to arginine-vasopressin (AVP). Here we have attempted to characterize further these inhibitory effects by studies of isolated perfused rat kidney and mesenteric vascular beds. In the isolated rat kidney, (-)-cicletanine behaves as a noncompetitive antagonist of AII- and AVP-receptor stimulation, with Ki values of 9.6 and 208 micromol/L respectively. In the isolated mesenteric vascular bed, (-)-cicletanine antagonized both AII dependent contractions with an inhibitory concentration (IC50) of 54.0 +/- 20.5 micromol/L (n = 6), and AVP dependent contractions with an IC50 of 31.6 +/- 5.0 micromol/L (n = 8). In conclusion, (-)-cicletanine antagonizes AII more effectively in rat kidney than in mesenteric vascular beds. Moreover, in rat kidney vascular beds (-)-cicletanine is more potent in blocking the pressor responses to AII than in blocking those to AVP. A selective blockade of AII induced contractions in kidney vascular beds can be one factor explaining both the greater antagonistic potency of (-)-cicletanine against AII compared with AVP in pithed rats, and the renal protective properties of cicletanine in both hypertensive and aged rats.

Angiotensin II↗

PubMed1998

The erythrocyte Na,K,Cl cotransporter and its circulating inhibitor in Dahl salt-sensitive rats.

BACKGROUND: Abnormal Na,K,Cl cotransport is thought to be a pathogenic factor in Dahl salt-sensitive rat models, but the only direct evidence for this is an increased cotransport activity found in erythrocytes from salt-loaded Dahl salt-sensitive rats. OBJECTIVE: To re-examine erythrocyte cotransport fluxes and a circulating cotransport inhibitory factor (CIF) in inbred Dahl rats maintained on a low (0.2%) salt diet. Cotransport fluxes were investigated both under basal conditions and after stimulation by cell shrinking. METHODS: Blood was drawn from 12 male Dahl salt-sensitive and 12 Dahl salt-resistant rats of the inbred John Rapp strain. Erythrocyte Na,K,Cl cotransport activity was equated to the bumetanide-sensitive fluxes of sodium, rubidium or lithium. Plasma CIF activity was tested in human erythrocytes. RESULTS: In Dahl salt-sensitive rats: (1) plasma CIF activity (5.7+/-0.4 units/ml) was modestly higher than in Dahl salt-resistant rats (2.97+/-0.12 units/ml, P < 0.0001), but much lower than that previously found in salt-loaded Dahl salt-sensitive rats (16.1 units/ml), and (2) erythrocytes exhibited a similar bumetanide-sensitive sodium efflux (rate constant 0.056+/-0.008 h(-1)) as in Dahl salt-resistant rats (0.047+/-0.007 h(-1)). Following hypertonic shock, the bumetanide-sensitive rubidium influx reacted more to cell shrinkage in Dahl salt-sensitive than in Dahl salt-resistant erythrocytes (cell volume decrease required to stimulate bumetanide-sensitive rubidium influx by 4000 micromol/l cells per h=-4.04+/-0.36 versus -5.89+/-0.44 fl, respectively; P< 0.01). CONCLUSIONS: When fed a low-salt diet, Dahl salt-sensitive rats present slightly increased plasma CIF levels and normal erythrocyte cotransport fluxes under basal conditions, but an increased response to a hypertonic shock. Therefore, if there is any primary cotransport abnormality in Dahl salt-sensitive rats, it appears to be restricted to the renal Na,K,Cl cotransporter BSC1 isoform. Alternatively, any such change may be the consequence of abnormal regulation by osmolarity-dependent mechanisms.

Animals↗

PubMed1998

In vitro antioxidant properties of calcium dobesilate.

Calcium dobesilate, a vascular protective agent, was tested in vitro for its scavenging action against oxygen free radicals. Calcium dobesilate was as potent as rutin to scavenge hydroxyl radicals (IC50 = 1.1 vs 0.7 microM, respectively). It was also able to scavenge superoxide radicals, but with 23 times less potency than rutin (IC50 = 682 vs 30 microM, respectively). Calcium dobesilate significantly reduced platelet activating factor (PAF)-induced chemiluminescence in human PMN cells and lipid peroxidation by oxygen free radicals in human erythrocyte membranes, although these actions required calcium dobesilate concentrations > or = 50 microM. Finally, in cultured bovine aortic endothelial cells, magnesium dobesilate reduced the increase in cytosolic free calcium induced by hydrogen peroxide and inhibited phenazine methosulfate-induced cell potassium loss. In conclusion, calcium dobesilate was effective in scavenging hydroxyl radicals in vitro, at therapeutically relevant concentrations. Conversely, higher concentrations of the compound were required to scavenge superoxide radicals or to protect the cells against the deleterious effects of intracellular reactive oxygen species. Further studies in vivo are required to determine if these antioxidant properties of calcium dobesilate can play a role in its vascular protective mechanisms.

Animals↗

PubMed1998

Salidiuretic action by genistein in the isolated, perfused rat kidney.

The urinary isoflavonoid genistein inhibits membrane Na-K-Cl cotransporters at similar concentrations as furosemide, but the significance of this action is unknown. Genistein was therefore investigated in rats for its potential salidiuretic actions. In the isolated, perfused rat kidney, genistein induced a maximal salidiuretic action similar to that of furosemide but was 3 to 5 times less potent than furosemide in terms of active doses (natriuresis EC50, 237+/-92 versus 56+/-20 micromol/L for genistein and furosemide, respectively). Genistein and furosemide had no additive salidiuretic actions. Genistein had no significant effect on glomerular filtration rate but was able to significantly reduce renal vascular resistance with respect to vehicle isolated perfused kidney. Indomethacin (10 micromol/L), a blocker of prostaglandin biosynthesis, reduced salidiuresis and renal vasorelaxation by genistein. Subcutaneous genistein (15 mg/kg) induced a statistically significant increase in diuresis and natriuresis with respect to vehicle during the first 6 hours of administration in rats. In conclusion, genistein compares well with furosemide in vitro for its salidiuretic profile and potency in the isolated perfused rat kidney and is also natriuretic by the subcutaneous route in the rat. Further studies are required to investigate potential natriuretic and perhaps hypotensive actions of dietary genistein.

Animals↗

PubMed1997

Fenspiride and membrane transduction signals in rat alveolar macrophages.

Fenspiride inhibits the calcium signal evoked by the inflammatory peptide formyl-Met-Leu-Phe (fMLP) in peritoneal macrophages, but at concentrations (approximately 1 mM) far above the therapeutic range (approximately 1 microM). Here, in rat alveolar macrophages, high fenspiride concentrations (1 mM) were required to inhibit the calcium signals evoked by the calcium agonist Bay K8644 or by ionomycin. Moreover, fenspiride (1 mM) was a poor inhibitor of the cell membrane depolarization induced by gramicidine D. By contrast, fenspiride blocked Na+-H+ antiport activation by (i) fMLP with an IC50 = 3.1 +/- 1.9 nM and (ii) PMA (phorbol 12-myristate 13-acetate) with an IC50 = 9.2 +/- 3.1 nM. Finally, protein kinase C (PKC) activity of macrophage homogenate was not significantly modified by 10 or 100 microM fenspiride (at 100 microM: 2.57 +/- 1.60 vs. 2.80 +/- 1.71 pmol/10(6) cells/min). In conclusion, fenspiride inhibits fMLP- and PMA-induced pH signals in rat alveolar macrophages, probably by acting distally on the PKC transduction signal. This pH antagonistic action may be relevant for the antiinflammatory mechanism of fenspiride and requires further investigation.

Animals↗

PubMed1997

Inhibition by xipamide of amiloride-induced acidification in cultured rat cardiocytes.

The diuretic drug xipamide improves myocardial relaxation in hypertensive patients with left ventricular hypertrophy, but its mechanism of action is unknown. Here, xipamide was tested in cultured rat heart myogenic H9c2 cells and newborn cardiomyocytes for its effects on cell acidification (and Ca2+ mobilization). In H9c2 cells, blocking Na+/H+ exchange with amiloride (2 mM) provoked cell acidification with rate = 0.82 +/- 0.17 pH units/h (n = 6). Xipamide 1 microM maximally inhibited 50 +/- 7% (n = 9) of cell acidification. The action of xipamide required the presence of HCO3- and was antagonized by the HCO3(-)-transport blocker DIDS (4,4'-diisothiocyanostilbene-2.2'-disulfonic acid). Conversely, the carbonic anhydrase (EC 4.2.1.1) inhibitor acetazolamide failed to prevent xipamide action. Finally, xipamide was without significant effect on the Ca2+ signals induced by endothelin-1, vasopressin or the Ca2+ ionophore ionomycin. In newborn rat cardiomyocytes, xipamide reduced amiloride-induced cell acidification at similar concentrations as in H9c2 cardiocytes, but with a slightly higher extent of maximal inhibition (70-80%). In conclusion, xipamide reduced amiloride-dependent cell acidification in the rat heart myogenic H9c2 cell line and in newborn rat cultured cardiomyocytes. This action of xipamide seems to be related to a complex interaction with DIDS-sensitive HCO3- movements. Prevention of cell acidification by xipamide could be involved in the beneficial effects of this compound in myocardial relaxation and left ventricle filling in hypertensive patients with left ventricular hypertrophy.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗