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R Garay

Publications and source records attributed to R Garay.

At least 55 records · Page 3Linked to original sources
PubMed1988

Sodium transport kinetics in erythrocytes from spontaneously hypertensive rats.

Rat erythrocytes with five different amounts of Na+ content have been prepared by using a new, nondetrimental Na+-loading method (net NaHPO4-influx through the anion carrier). This method allowed the determination of 1) maximal translocation rates and apparent dissociation constants for internal Na+ of the Na+-K+ pump, outward Na+-K+ cotransport, and Na+-Li+ countertransport and 2) rate constants of Na+ leak in erythrocytes from spontaneously hypertensive rats of the Okamoto strain and Wistar-Kyoto normotensive controls aged 2 to 26 weeks. Two major abnormalities were found in erythrocytes from spontaneously hypertensive rats: 1) a decreased cotransport affinity for internal Na+, which was constantly observed from 2 to 26 weeks of age (mean intracellular Na+ content for half-maximal stimulation of outward Na+-K+ cotransport = 33.1 +/- 7.0 [SD] mmol/L cells in spontaneously hypertensive rats vs 16.7 +/- 4.7 mmol/L cells in Wistar-Kyoto rats; p less than 0.001), and 2) a decreased maximal pump rate in adult (15- to 26-week-old) spontaneously hypertensive as compared with that for age-matched Wistar-Kyoto rats (9-37 vs 34-70 mmol/L cells/hr). Therefore, the low cotransport affinity for internal Na+ appears to be a stable, possibly genetic defect of spontaneously hypertensive rats. Conversely, the decreased maximal pump rate may be a secondary event, possibly reflecting the appearance of endogenous pump inhibitors in the plasma of adult spontaneously hypertensive rats.

Age Factors↗
PubMed1988

[Antihypertensive effects of captopril, hydrochlorothiazide, alone or in combination, with different categories of essential hypertensive patients].

30 male essential hypertensive patients were submitted to a "washout" of 8 days and at D (0) divided into two groups receiving 25 mg/day of Hydrochlorothiazide or 50 mg/day of Captopril. At D (45) the treatment was crossed, at D (90) all the patients received both drugs and at D (135) the treatment was stopped. According to the antihypertensive response, the patients were divided into: (i) R: responders, PAS (systolic arterial pressure) less than or equal to 140 mmHg and PAD (diastolic) less than or equal to 90 mmHg, ii) M: moderate responders, 140 less than PAS less than or equal to 160 mmHg and/or 90 less than PAD less than or equal to 100 mmHg and (iii) F: therapeutic failure, PAS greater than 160 mmHg and/or PAD greater than 100. A parallel study was carried out in erythrocytes. At D (0), 40 ml of blood were drawn and the hypertensive patients were classified in: (i) (+)NaT patients, 19 patients having one or more of the following erythrocyte abnormalities: increased Na+: Li+ counter-transport, increased Na+ leak, decreased affinity of the Na+, K+-pump and/or Na+, K+ cotransport system for internal Na+ and (ii) (-)NaT patients, 11 patients without the above erythrocyte abnormalities. During monotherapy treatment (with captopril or hydrochlorothiazide) 8 out of 11 (-)NaT patients normalized blood pressure (responders) against only 5 out of 19 (+)NaT patients (p less than 0.05, chi 2 test).(ABSTRACT TRUNCATED AT 250 WORDS)

Biological Transport↗
PubMed1987

A one-to-one Mg2+:Mn2+ exchange in rat erythrocytes.

Mg2+ efflux in rat erythrocytes was stimulated by increases in external Na+ concentration following a Michaelian-like function with an apparent dissociation constant (KNa) of 11 +/- 3 mM (mean +/- S.D. of three experiments) and a variable maximal rate ranging from 150 to 1200 mumol (liter (1) cells X h)-1. Na+-stimulated Mg2+ efflux was inhibited by quinidine and by ATP depletion. In the absence of external Na+, Mg2+ efflux was stimulated by increases in external Mn2+ concentration following a Michaelian-like function with an apparent dissociation constant (KMn) of 35 +/- 15 microM (mean +/- S.D. of four experiments) and a variable maximal rate ranging from 350 to 1400 mumol (1 cells X h)-1. Mn2+-stimulated Mg2+ efflux was inhibited by quinidine, by ATP depletion, and by increasing the external Na+ concentration. Quinidine-sensitive (or ATP-dependent) Mg2+ efflux exhibited very similar values when compared with quinidine-sensitive (or ATP-dependent) Mn2+ influx. Mn2+ efflux in rat erythrocytes (loaded with total internal Mn2+ contents of 230-450 mumol/l cells) was stimulated by increases in external Na+ concentration and inhibited by quinidine. In the absence of external Na+, Mn2+ efflux was stimulated by increases in external Mg2+ concentration following a Michaelian-like function with an apparent dissociation constant (KMg) of about 35 +/- 5 microM (mean +/- range of two experiments) and a maximal rate of about 60-100 mumol (1 cells X h)-1. In conclusion, the Na+-stimulated Mg2+ carrier of rat erythrocytes may catalyze a one-to-one and reversible Mn2+:Mg2+ exchange in the absence of external Na+.

Animals↗
PubMed1987

Sodium transport in primary hypertension.

Humans and rats with primary hypertension may exhibit different and stable abnormalities in membrane Na+ transport systems: (i) Pump (-) = decreased apparent affinity of the pump for internal Na+, (ii) Co (-) = decreased apparent affinity of the Na+, K+ cotransport system for internal Na+ (iii) Leak (+) = increased passive Na+ permeability and (iv) = Counter (+) abnormality (increased maximal rate of Na+-Li+ and perhaps Na+-H+ exchange). Excess Na+ intake tends to be compensated by the transient secretion of endogenous "digitalis-like" and other natriuretic factors. The presence of Co(-) or Leak(+) abnormalities may amplify transitory cell Na+ rises induced by endogenous digitalis-like factors at the vascular wall. The Counter(+) abnormality may increase renal Na+ reabsorption and induce permanent hypersecretion of endogenous digitalis-like factors.

Animals↗
PubMed1986

Involvement of K+ movements in the membrane signal induced by PAF-acether.

We investigated the effects of PAF-acether and its specific antagonist BN 52021 on Na+ and K+ transport systems in human red cells and mouse macrophages. PAF-acether and BN 52021 exhibited specific and opposite effects on a Cs+-stimulated, K+ efflux in human red cells. PAF-acether increased and BN 52021 decreased the apparent dissociation constant for external Cs+ without significant effects on the maximal rate of K+ translocation. In mouse macrophages, PAF-acether stimulated a quinidine-sensitive K+ efflux. In the presence of the Ca2+-ionophore A 23187, PAF-acether and BN 52021 showed opposite effects (stimulation and inhibition respectively). For most cells, membrane potential is dependent on K+-permeability. In addition, opening of potential-dependent Ca2+ channels appears to be associated with cell activation in several models. We thus propose that the specific interaction of PAF-acether with a K+:K+ exchange increases Ca2+ uptake through transitory changes in membrane potential. This in turn may lead to a more permanent membrane hyperpolarization through to opening of Ca2+ dependent, K+ channels.

Animals↗
PubMed1986

An Na+-stimulated Mg2+-transport system in human red blood cells.

The initial rate of net Mg2+ efflux was measured in human red blood cells by atomic absorption. In fresh erythrocytes incubated in Na+,K+-Ringer's medium this rate was 7.3 +/- 2.8 mumol/l cells per h (mean +/- S.D. of 14 subjects) with an energy of activation of 13 200 cal/mol. Cells with total Mg2+ contents ([ Mg]i) ranging from 1.8 to 24 mmol/l cells were prepared by using a modified p-chloromercuribenzenesulphonate method. Mg2+ efflux was strongly stimulated by increases in [Mg]i and in external Na+ concentrations ([ Na]o). A kinetic analysis of Mg2+ efflux as a function of [Mg]i and [Na]o revealed the existence of two components: an Na+-stimulated Mg2+ efflux, which exhibited a Michaelian-like dependence of free internal Mg2+ content (apparent dissociation constant = 2.6 +/- 1.4 mmol/l cells; mean +/- S.D. of six subjects) and on external Na+ concentration (apparent dissociation constant = 20.5 +/- 1.9 mM; mean +/- S.D. of four subjects) and a variable maximal rate ranging from 35 to 370 mumol/l cells per h, and an Na+-independent Mg2+ efflux, which showed a linear dependence on internal Mg2+ content with a rate constant of (6.6 +/- 0.7) X 10(-3) h-1. Fluxes catalyzed by the Na+-stimulated Mg2+ carrier were partially dependent on the ATP content of the cells and completely inhibited by quinidine (IC50 = 50 microM) and by Mn2+ (IC50 = 0.5-1.0 mM).

Adenosine Triphosphate↗
PubMed1986

Stimulation of beta-adrenoceptors inhibits calcium-dependent potassium-channels in mouse macrophages.

K+ efflux in mouse macrophages exhibited a rate constant (kK) of 0.67 +/- 0.04 (h)-1 (mean +/- SEM of 16 experiments). This was strongly stimulated by increasing concentrations of the Ca2+ ionophore A23187 up to a maximal value of 4.01 +/- 0.25 (h)-1 with an IC50 of 7.6 +/- 1.9 microM (mean +/- SEM of 6 experiments). Similar results were obtained with the Ca2+ ionophore ionomycin. Binding experiments with 3H-dihydroalprenolol revealed a high density of beta-adrenergic receptors (97.5 +/- 5.2 fmol/mg protein) with apparent dissociation constant of 2.03 +/- 0.06 nM. Isoproterenol at a concentration of 10(-6)-10(-5) M induced a two- to threefold stimulation of endogenous levels of cyclic AMP (cAMP). A23187-stimulated K+ efflux was partially inhibited by stimulation of adenylate cyclase with isoproterenol, forskolin or, PGE1; exogenous cAMP; and inhibition of phosphodiesterase with MIX (1-methyl-3-isobutylxanthine). Maximal inhibition of K+ efflux was obtained by simultaneous addition of isoproterenol and MIX. In dose-response curves, the isoproterenol-sensitive K+ efflux was half-maximally inhibited (IC50) with 2-5 X 10(-10) M of isoproterenol concentration. Propranolol was able to completely block the effect of isoproterenol, with an IC50 of about 1-2 X 10(-7) M. Isoproterenol and MIX were also able to partially inhibit ionomycin-stimulated K+ efflux. Isoproterenol and MIX did not inhibit A23187-stimulated K+ efflux in an incubation medium where NaCl was replaced by sucrose (or choline), suggesting the involvement of an Na+:Ca2+ exchange mechanism. Our results show that stimulation of beta-adrenoceptors in mouse macrophages counterbalances the opening of K+ channels induced by the calcium ionophore A23187. This likely reflects a decrease in cytosolic free calcium content via a cAMP-mediated stimulation of Na+:Ca2+ exchange.

1-Methyl-3-isobutylxanthine↗
PubMed1986

Inhibition of the erythrocyte Na+, K+-pump by mammalian lignans.

Several mammalian lignans, particularly enterolactone, 3-oxy-methyl enterolactone and prestegane B are able to inhibit Na+, K+-pump activity in human red cells with IC50 of about 1 mM. The inhibition of Na+, K+-pump activity by mammalian lignans have the following properties: the IC50 for ouabain remains unchanged suggesting a noncompetitive inhibition. The apparent affinity for internal Na+ and maximal rate of cation translocation are both diminished. The above inhibition of the Na+, K+-pump was obtained at doses 2-3 orders of magnitude higher than those required for ouabain. However we cannot exclude that a glycosyl- (and/or butenolide)-derivative of enterolactone could be one endogenous ouabain-like factor.

Cross Reactions↗
PubMed1986

Effect of canrenone on the disturbances of cation handling induced by ouabain in macrophages and vascular smooth muscle cells.

Ouabain induced rapid and profound modifications of Na+ and K+ contents in mouse macrophages and cultured vascular smooth muscle cells. In mouse macrophages, we found a one-to-one net Na+ gain and K+ depletion, with a maximal initial rate of 30 to 35 mmol (l X cells X hr)-1 and with an IC50 of about 100 microM. The one-to-one exchange results from at least two additive effects: inhibition of the Na+,K+-pump and stimulation of a furosemide-sensitive, outward Na+,K+-cotransport by the increase in internal Na+ content. The latter effect helps the cell to maintain a normal cell volume in spite of the large changes in internal cation content. In cultured vascular smooth muscle cells from rat aorta, ouabain provoked net Na+ gain and stimulated a quinidine-sensitive, K+-efflux. This likely reflects the opening of Ca+-dependent, K+-channels in response to an increase in cytosolic-free Ca+ content. Canrenone, an antihypertensive drug, has been shown to behave like a partial agonist at the digitalisreceptor site of the Na+,K+-pump. We observed here in mouse macrophages and cultured vascular smooth muscle cells that: canrenone alone (or at low ouabain concentrations) induces slight Na+ gain and K+ depletion; canrenone partially counterbalances the very rapid cell Na+ gain (and K+ depletion) provoked by high ouabain concentrations, and canrenone reverses the secondary effects of ouabain on the Na+,K+-cotransport system and Ca+-dependent, K+-channels. It appears therefore that canrenone may partially reverse the disturbances of cation handling induced by high concentrations of ouabain in macrophages and vascular smooth muscle cells.

Animals↗
PubMed1986

[Mammalian lignans: possible involvement in endogenous digitalis activity].

Lignans are natural products, some of which were recently discovered in animal urines, semen and blood plasma. We investigated the actions of animal lignans obtained by total synthesis or extracted from urines of pregnant women on Na+, K+-ATPase in human red cells and human and guinea-pig heart cell membranes. Some of the tested lignans (enterolactone, prestegane B and 3-O-methyl enterolactone) inhibited Na+, K+-pump activity in human red cells with IC50 ranging from 5 to 9 X 10(-4) M. The IC50 for ouabain (7 X 10(-7) M) was not modified by addition of lignans. Enterolactone inhibited Na+, K+-ATPase activity in human and guinea pig heart membranes. It also displaced [3H]-ouabain binding from human heart with IC50 = 1.5 X 10(-4) M. The apparent dissociation rate constants (kd) of [3H]-ouabain were not different in presence of digoxin or enterolactone. Enterolactone exhibited a poor cross reactivity against antidigoxin antibodies. The aglycones of the lignans studied here were slight inhibitors of the Na+, K+-ATPase. However, we cannot exclude that a glycosyl- (and/or butenolide-) derivative of enterolactone could be one "endogenous ouabain-like" factor.

Animals↗
PubMed1985

Leukocytic functions in burn-injured patients.

Anergy associated with an increase in suppressor helper T cell (Tc) ratio and a decrease in natural killer (NK) is one main cause of death following thermal injury (Tl). Recently, in vitro studies have shown that LTB4 can induce human Tc to exert suppressor cell activity, and incubation of lymphocytes with LTB4 for 24 hours significantly suppressed NK cell activity. Thus, we undertook an investigation of both AA metabolism and immunologic response in 20 patients who suffered 40-90% total body surface area (TBSA) burns. Cyclooxygenase (CO:RIA) and lipoxygenase (LO;HPLC det.) metabolites and superoxide (O2 X-) production were measured in stimulated polymorphonuclear cells (PMNL) (A 23187 +/- AA for icosanoid release; phorbol myristate acetate for O2 X-production). Lyso-paf-acether (P-LPA) was measured in plasma samples. Ca2+-dependent K+permeability in PMNL was measured by the cell K+ release induced by A 23187. Tc and Tc subsets were determined using monoclonal antibodies (OKT3+, OKT4+ and OKT8+). A biphasic sequential release of the different substances (leukocytic icosanoids and O2 X-) was monitored: increase (approximately 36-48 h after Tl) and decrease (greater than or equal to 72 h after Tl). The increase in AA stimulation was more transient than that of O2 X -. The decline in the release of AA metabolites and O2 X-production was associated with the anergic phase (decrease OKT4+/OKT8+ ratio) and with the clinical outcome of the patients. The decrease in LTB4 and other LO metabolites could explain the impairment of neutrophil chemotaxis. Ca2+-dependent K+ permeability increased early up to 2 or 3 times normal. In order to go further with the mechanism of inhibition of LTB4 and O X-release, the effect of Tl plasma was assayed on normal leukocytes: a 10 min incubation with such plasma was sufficient to abolish LTB4 secretion. A less important inhibition was observed with O2 X-release (-32%) and Ca2+-dependent K+ permeability (-30%). Plasma inhibition seems to be due to a thermolabile factor(s) [protein(s): "suppressive factor(s) of membrane activation "SFMA] which is (are) under active investigation using gel-filtration chromatography and fast protein liquid chromatography (FPLC). Among the SFMAs, certain acute phase proteins could play a key role: i.e., incubation (10 min) of normal PMNL with ceruloplasmin (1 mg/ml) abolished LO products and O X 2-release.

Adolescent↗
PubMed1985

A classification of essential hypertensive patients according to the erythrocyte Na transport abnormalities: an application for monitoring the antihypertensive response to cicletanide.

We have studied the kinetic properties of the interaction of internal Na with four different Na transport pathways (ouabain-sensitive Na, K pump, bumetanide-sensitive Na,K cotransport, Li:Na countertransport and passive Na permeability) in erythrocytes from 197 essential hypertensive patients. This study permitted us to classify 168 of the 197 hypertensives studied into the following groups: Pump - hypertensives-six patients showing low pump affinity for internal Na and high maximal pump rate; Co - hypertensives -95 patients characterized by low cotransport affinity for internal Na and low or normal maximal outward cotransport rate. Counter + hypertensives - 35 patients characterized by low countertransport affinity for internal Na and high maximal countertransport rate; and Leak + hypertensives - 32 patients showing increased passive Na permeability. Having studied the apparent affinity of the Na,K cotransport system for external K we divided the co - hypertensives into three subgroups (symmetric, asymmetric or antisymmetric) according to the presence of low, normal or high K affinity. Forty-five hypertensive patients were submitted to antihypertensive treatment with a new diuretic and antihypertensive drug, cicletanide. Preliminary results indicate that one of the factors involved in the antihypertensive efficiency of the compound is the subgroup to which the hypertensive belongs.

Adult↗
PubMed1985

Atrial natriuretic factor inhibits Ca(2+)-dependent K+ fluxes in cultured vascular smooth muscle cells.

The interaction of the synthetic fragment Arg101-Tyr126 of atrial natriuretic factor (ANF) with Ca(2+)-dependent K+ efflux was studied in the following six different cell models: cultured vascular smooth muscle cells from rat aorta; isolated rat glomeruli; human platelets; cultured endothelial cells from bovine aorta; peritoneal mouse macrophages; human red cells. In human red cells and mouse macrophages, the dose-response curves of K+ efflux as a function of Ca2+ ionophore, A23187, concentration were not modified by addition of ANF. In endothelial cells and platelets, ANF slightly inhibited Ca(2+)-dependent K+ efflux. In renal glomeruli, ANF inhibits about one-third of this flux and in vascular smooth muscle cells ANF induced a five- to tenfold increase in the EC50 of A23187 effect. In experiments performed at constant concentrations of A23187, the IC50 of ANF was approximately 10(-9) mol/l. Similar results were obtained in mouse macrophages with cyclic GMP (cGMP). Our results suggest that ANF is able to counterbalance an increase in cytosolic free Ca2+ content in vascular smooth muscle and some glomerular cells. This effect may result from the ability of this hormone to stimulate cGMP synthesis.

Animals↗
PubMed1985

Hypotensive action of canrenone in a model of hypertension where ouabain-like factors are present.

It has been proposed that peripheral resistance can be increased by ouabain-like factors that are able to increase cell sodium and thereby cell calcium. Canrenone has been reported to be a partial agonist of ouabain. The effect of canrenone was investigated in rats with reduced renal mass (RRM) showing evidence of excess circulating ouabain-like factors. Wistar rats were uninephrectomized, 30% of the other kidney was removed, and they were given a 0.8% NaCl solution to drink. Half of them received 60 mg/kg per day of canrenone orally for 26 days. In RRM, the following indices of a ouabain-like activity were found: erythrocyte Na+K(+)-pump activity was decreased by 39% (P < 0.001), sodium content increased by 12% (P < 0.01), net erythrocyte sodium extrusion in plasma decreased by 20% (P < 0.01), and plasma digoxin equivalents increased by 62% (P < 0.02). Canrenone increased the IC50 for ouabain from 1.05 to 2.16 x 10(-4) mol/l (P < 0.05) in erythrocytes. In RRM with systolic blood pressure of 165 mmHg, acute administration of canrenone decreased blood pressure by 36 mmHg. Chronic administration blunted the blood pressure rise by 12, 26 and 21 mmHg at days 5, 14 and 26, respectively (P < 0.05). Haematocrit was markedly reduced in RRM (33%) and much less when treated with canrenone (37.5%). In conclusion, in contrast with spontaneously hypertensive rats, RRM hypertension is a model where a ouabain-like factor is present and in which canrenone reduces blood pressure. The hypotensive effect of canrenone may be related to a competition with ouabain-like factors.

Animals↗