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Biomedical subjects

R Marín

Publications and source records attributed to R Marín.

At least 73 records · Page 4Linked to original sources
PubMed1988

Na-pump activity in rat kidney cortex cells and its relationship with the cell volume.

The present work was undertaken to evaluate whether changes in cell water content of rat kidney cortex cells can modulate the transport activity of the ouabain-insensitive Na pump as they modulate the ouabain-insensitive Na+-ATPase. It was found that there is a close relationship between the cell volume and activity of the Na pump, whereas Na,K-pump activity is not affected by variations in cell volume. When the cell water content is low, Na-pump activity (Na+ transport and Na+-ATPase activity) is minimal. Increases in cell water content produce a concomitant increase in Na-pump activity.

Adenosine Triphosphatases↗
PubMed1988

Cell volume-sensitive Na+-ATPase activity in rat kidney cortex cell membranes.

A ouabain-insensitive, K+-independent, sodium pump, has been demonstrated in guinea-pig and rat kidney proximal tubular cells. This pump is thought to be distinct from the ouabain-sensitive Na+/K+ pump. We present evidence here indicating the modulation of the biochemical expression of the Na+ pump, i.e. the ouabain-insensitive Na+-ATPase, by the cell volume in rat kidney proximal tubular cells. Thus, basolateral plasma membranes from swollen cells show a ouabain-insensitive Na+-ATPase activity 10-times higher than that in membranes from control cells. If the swollen cells recover their volume, the activity decreases ten times to control values. The ouabain-sensitive Na+/K+-ATPase is not affected by changes in the cell volume.

Adenosine Triphosphatases↗
PubMed1987

High sodium diet and Na+-stimulated ATPase activities in basolateral plasma membranes from rat kidney proximal tubular cells.

The ouabain-insensitive, Na+-stimulated ATPase activity of kidney proximal tubular cells from rats fed a high Na+ diet for 4 months was increased approximately 70% when compared with control (normal diet) rats. The higher ATPase activity was not due to a change in the affinity of the system toward ATP, Mg2+ or Na+. This increase in Na+-ATPase activity may be due to either a higher number of pumps or to a higher turnover rate of the enzyme or both. The ouabain-sensitive, Na+, K+-stimulated ATPase activity, on the other hand, did not change with the high sodium diet. These results can be taken as evidence that the Na+,K+-ATPase and the Na+-ATPase of basolateral plasma membranes of proximal tubular cells from rat kidney are two different entities.

Adenosine Triphosphatases↗
PubMed1987

[The presence of cysts in Tritrichomonas muris].

Cysts of Tritrichomonas muris are reported. The morphology of this evolution stage is described under light and electron microscopy. The biologic and epidemiologic importance of this finding is discussed.

Animals↗
PubMed1986

Inside-out basolateral plasma membrane vesicles from rat kidney proximal tubular cells.

A method for preparation of highly purified basolateral plasma membranes from rat kidney proximal tubular cells is reported. These membranes were assayed for the presence of vesicles as well as for their orientation. (Na+ + K+)-ATPase activity and [3H]ouabain binding studies with membranes treated with or without SDS revealed that the preparation consisted of almost 100% vesicles. The percentage of inside-out vesicles was found to be approx. 70%. This percentage was determined measuring the (Na+ + K+)-ATPase activity in K+-loaded vesicles and in membranes treated with or without trypsin and SDS. These membranes represent a very efficient tool to assay the correlation between active transport and ATPase activities in basolateral plasma membranes from rat kidney proximal tubular cells.

Animals↗
PubMed1986

Na+-ATPase is a different entity from the (Na+ + K+)-ATPase in rat kidney basolateral plasma membranes.

In this work, we present evidence in agreement with the hypothesis that there exist two Na+-stimulated ATPase activities in basolateral plasma membranes from rat kidney proximal tubular cells: (1) (Na+ + K+)-ATPase activity, which is inhibited by ouabain and by treating the membranes with trypsin, is insensitive to furosemide and reaches maximal activity upon treatment with SDS at an SDS/protein ratio of 1.6; (2) the Na+-ATPase activity, which is insensitive to ouabain and to trypsin treatment, is inhibited by furosemide and reaches maximal activity upon treatment with SDS at an SDS/protein ratio of 0.4.

Adenosine Triphosphatases↗
PubMed1986

Effect of a high NaCl diet on the active mechanisms of Na+ extrusion in rat kidney.

Healthy male rats were exposed to a chronic ingesta of an isotonic NaCl solution during a period of four months. Two different preparations were utilized to study the effect of this treatment on the active mechanisms of Na+ reabsorption of kidney proximal tubular cells: outermost kidney cortex slices (rich in proximal tubules) and inside-out basolateral plasma membrane vesicles prepared from the same tissue. It was found that the activity of the ouabain-insensitive, Na-pump of basolateral plasma membranes of kidney proximal tubular cells was increased in about 70%, whereas the ouabain-sensitive, Na,K-pump activity did not change with the experimental treatment. These results represent a strong support to the two Na-pump's hypothesis since the treatment affected the Na-pump differentially without affecting the Na,K-pump.

Absorption↗
PubMed1985

Characterization of the Na+, K+-ATPase activity of basolateral plasma membranes of kidney proximal tubular cells from young and old rats.

Several characteristics of the Na+, K+-ATPase activity of basolateral plasma membranes of kidney proximal tubular cells from young (3 months) and old (24 months) rats were studied. In both cases, the ATPase activity reached optimum values under the following conditions: Mg2+:ATP concentrations (mM) 5:5 (apparent Km 0.5 mM); Na+ concentration 50 mM (apparent Km 18 mM); K+ concentration 20 mM (apparent Km 2.5 mM); pH 7.2; temperature 52 degrees. The values of the apparent energy of activation of the system were similar for young and old rats in the temperature range 20-52 degrees but were 55% higher for the old rats in the temperature range 10-20 degrees.

Age Factors↗
PubMed1985

Effect of Ca2+ on the ouabain-insensitive, active Na+ uptake in inside-out basolateral plasma membrane vesicles from rat kidney proximal tubular cells.

The ouabain-insensitive, active Na+ uptake of inside-out vesicles prepared with basolateral plasma membranes from rat kidney proximal tubular cells can be increased by the presence of micromolar concentrations of Ca2+ in the assay medium. The concomitant ATP hydrolysis associated with the Na+ uptake is also increased by the presence of Ca2+. The Na+ uptake and the concomitant ATP hydrolysis are inhibited by 2 mM furosemide. The effect of Ca2+ is not due to the activity of an Na+-Ca2+ exchanger. The present results are in accordance with our previous model (Proverbio, F., Proverbio, T. and Marín, R. (1982) Biochim. Biophys. Acta 688, 757-763) in which we proposed that Ca2+ seems to modulate the activity of the ouabain-insensitive Na+ pump, in two different ways: (1) in a strong association with the membranes in which Ca2+ (stable component) is essential for the pump activity and (2) in a weak association with the membranes in which Ca2+ (labile component) can be quickly and easily removed by reducing the free Ca2+ concentration of the assay medium to values lower than 1 microM. The Ka for Ca2+ (for the labile component) is around 5 microM. The Ca2+ modulation of the ouabain-insensitive Na+ pump is an indication that Ca2+ could regulate the magnitude of the Na+ extrusion accompanied by Cl- and water present in rat kidney proximal tubular cells.

Adenosine Triphosphate↗
PubMed1985

ATPase activities in kidney basolateral plasma membranes of young and old rats.

The present work studied the turnover rate of (Na+ + K+)-ATPase as well as Mg2+- and Na+- ATPase activities in basolateral plasma membranes from kidney cortex cells of young and old rats. It was found that, as for the homogenates, the turnover rate of the (Na+ + K+)-ATPase was diminished by aging in about 40%. The Mg2+-ATPase activities on the other hand, were similar for the rat kidneys of young and old, in both the homogenates as well as the basolateral plasma membrane fractions.

Adenosine Triphosphatases↗
PubMed1985

Active sodium transport in basolateral plasma membrane vesicles from rat kidney proximal tubular cells.

Inside-out vesicles prepared with basolateral plasma membranes from rat kidney proximal tubular cells can accumulate Na+ actively in two ways. Mode 1, which is K+-independent, is ouabain-insensitive and is inhibited by furosemide and mode 2, which is K+-dependent, is inhibited by ouabain and is insensitive to furosemide. The presence of Mg2+ and ATP in the incubation medium is essential for both modes of Na+ uptake to proceed and in both cases, the nucleotide is hydrolyzed during the process. These results are consistent with the idea of the existence, in these membranes, of two Na+ pumps: one, which can work in the absence of K+ (Na+ pump) and another, which needs K+ to work (Na+ + K+ pump).

Animals↗
PubMed1985

Ion transport and oxygen consumption in kidney cortex slices from young and old rats.

The effects of aging on active Na+ extrusion and oxygen consumption associated with it were studied in rat kidney cortex cells. It was found that (a) the active extrusion of Na+ undergoing Na/K exchange and the active extrusion of Na+ with Cl- and water were diminished in old rats (24 months) as compared with young rats (3 months); (b) the oxygen consumption associated with each of the two active mechanisms of Na+ extrusion was also diminished in the old rats; (c) the calculated turnover rate of the Na/K pump was significantly lower for the old rats.

Aging↗
PubMed1984

Serum ferritin in haemodialysis patients: role of blood transfusions and 'haemochromatosis alleles' HLA A3, B7 and B14.

In 48 patients on maintenance haemodialysis (HD), serum ferritin (SF) levels were measured and compared with 'haemochromatosis alleles', (HA), HLA A3, B7 and B14. A positive correlation was found between high SF levels and the presence of HA. When patients who had received 10 or fewer blood transfusions were studied, it was observed that this correlation did not exist, but it was evident, however, in patients who had received more than 10 blood transfusions. After 14 months in which blood transfusions were restricted, no significant difference in SF was observed between HA carriers and the rest. Our findings suggest that repeated blood transfusions can cause high SF in HD patients, especially in those with HLA A3, B7 or B14 antigens. Among our patients, restriction of blood transfusions seems sufficient to decrease high SF levels.

Adolescent↗