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H J Rodriguez

Publications and source records attributed to H J Rodriguez.

At least 19 recordsLinked to original sources
PubMed1981

Regulation of renal Na+-K+-ATPase in the rat by adrenal steroids.

The effects of single and multiple injections of aldosterone and dexamethasone on renal Na+-K+-ATPase, in vitro renal gluconeogenesis, and urinary electrolyte excretion were examined in adrenalectomized rats in a dose-dependent manner. Single maximal and supramaximal doses of aldosterone (defined by the effect of electrolyte excretion) had no effect on Na+-K+-ATPase or gluconeogenesis. By contrast, a single administration of dexamethasone (in a dose range that increased fasting blood sugar, stimulated renal gluconeogenesis, and had no mineralocorticoid effects) yielded clear-cut activation of Na+-K+-ATPase. Multiple submaximal doses of dexamethasone produced quantitatively similar stimulation of Na+-K+-ATPase and gluconeogenesis. Multiple supramaximal doses of aldosterone stimulated Na+-K+-ATPase and gluconeogenesis, but maximal and submaximal doses of the hormone were without effect. Aldosterone had no effect on hepatic Na+-K+-ATPase or gluconeogenesis. These results suggest that activation of renal Na+-K+-ATPase can be considered a putative glucocorticoid (not mineralocorticoid) effect. Renal Na+-K+-ATPase activation by chronic aldosterone treatment may be mediated by glucocorticoid receptor sites and, hence, may not represent a genuine mineralocorticoid effect.

Adrenal Cortex Hormones↗
PubMed1980

Studies on amino acid incorporation in isolated toad bladder epithelial cells. Seasonal changes in protein synthesis.

Amino acid incorporation in isolated toad bladder epithelial cells was investigated by examining the rate of radiolabel incorporation into trichloroacetic acid-insoluble material. The results demonstrated that during the summer months, a large fraction of the radiolabel incorporated was not inhibited by cycloheximide and did not seem to correspond to incorporation of the radioactive amino acid into elongating peptides. A similar effect was not observed in other organs of the toad (e.g. liver, spleen). During the winter months, however, virtually all the acid-insoluble radiolabel appears to correspond to incorporation of the amino acid into elongating peptides. Ouabain, an inhibitor of sodium transport, inhibited amino acid incorporation into acid-insoluble material by affecting the acid-soluble pool and this effect appeared to be independent of the effect of ouabain on sidium transport. The isolated epithelial cells appeared to derive the energy for protein synthesis almost entirely from glycolysis and in this regard they resemble certain tissue culture cells.

Amino Acids↗
PubMed1980

Isolation of epithelial cells from toad bladder.

The epithelial cells of the toad bladder have been isolated by brief exposure to ethylenediaminetetraacetic acid followed by treatment with collagenase, DNAse, and the application of shearing forces. This approach eliminates the need for scraping of the mucosal surface and reduces mechanical damage during harvesting of the epithelium. The method yields intact, isolated epithelial cells and few clumps. The three major types of epithelial cells described in the intact toad bladder were present in the final preparation. The cellular contents of nucleic acids and proteins (in pg/cell) were: DNA 22.5 +/- 1.1; RNA, 12.9 +/- 0.6; and protein, 192 +/- 9. The isolated cells possess rates of oxygen consumption and amino acid incorporation higher than those of epithelial sheets obtained by collagenase treatment and scraping of the intact bladder. However, the production of cyclic nucleotides in response to stimulation by vasopressin and carbachol is comparable in both preparations.

Amino Acids↗
PubMed1980

Mechanism of activation of renal Na+-K+-ATPase in the rat: effects of potassium loading.

The mechanism of activation of Na+-K+-ATPase after chronic potassium loading has been investigated in the rat kidney. Potassium loading stimulated the specific activity of Na+-K+-ATPase in the cortex and medulla of the kidney. This effect was not accompanied by a generalized increase in the cellular contents of RNA and proteins and could not be accounted for by an effect of potassium loading on renal growth. Enzyme induction does not appear to be mediated by changes in the endogenous levels of glucocorticoid or thyroid hormones. Evidence obtained from investigation of the partial reactions (Pi intermediate, ouabain-sensitive pNPPase) of the Na+-K+-ATPase enzymatic reaction is consistent with the interpretation that chronic potassium loading in the rat increases the number of enzyme units (Na+ pumps) in the cortex of the kidney. Analysis of the kinetic parameters (Km, K1/2, Vmax, Hill coefficients) of the enzymatic reaction indicates that K+ loading has little or no effect on the kinetic properties (affinity, cooperativity) of the stimulated transport enzyme.

Animals↗
PubMed1980

Mechanism of activation of renal Na+-K+-ATPase in the rat: effects of reduction of renal mass.

The mechanism of activation of renal Na+-K+-ATPase was studied in rats 2 wk after unilateral nephrectomy. The increase in enzyme specific activity was confined to the outer medulla and occurred without changes in the cellular contents of RNA or protein. Enzyme activation was accompanied by increases in the levels of the phosphorylated intermediate with little or no change in the apparent turnover numbers of the reaction. The specific activity of the ouabain-sensitive p-nitrophenylphosphatase also increased by uninephrectomy but to a larger extent than did Na+-K+-ATPase. Kinetic studies demonstrated an increase in Vmax for ATP, sodium, and potassium, and small increases in Km for ATP and K1/2 for potassium. There was no change in the activation energies or phase transition temperature to indicate alterations in the membrane environment of Na+-K+-ATPase. Adrenalectomy did not adversely affect activation. These results indicate that activation of renal Na+-K+-ATPase after reduction of renal mass occurs mainly by an increase in the number of sodium pump sites.

Adenosine Triphosphate↗
PubMed1979

Radio-iodination of plasma membranes of toad bladder epithelium.

The present report describes high yield enzymatic radio-iodination of the apical and basal-lateral plasma membranes of toad bladder epithelium, by a procedure that does not breach the functional integrity of the epithelium, as assessed by the basal and vasopressin-sensitive short-circuit current (SCC). Restriction of the label to the membrane surface, was ascertained by light and electron-microscopic autoradiographs. On the apical surface, the grains were over the glycocalyx and the plasma membrane. Analysis of the labeled glycocalyx by agarose gel filtration, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), as well as enzymatic and pH-dependent hydrolysis indicated that the glycocalyx is a trichloro-acetic acid-soluble macromolecular complex of high molecular weight composed of a peptide moiety attached to large prosthetic groups (presumably carbohydrates) by O-glycosidic bonds. Analysis of the labeled apical plasma membrane components by agarose gel filtration and SDS-PAGE disclosed the presence of six major species of apparent molecular weights: 23,000, 28,000, 37,000, 44,000, 68,000, and 95,000. More than half of the membrane-associated radio-iodine was in two bands of molecular weights 37,000 and 44,000. Concentrations of vasopressin and cyclic AMP sufficient to increase the SCC significantly did not modify the extent of membrane labeling or the distribution of the label among the apical membrane components (presumably proteins) as assessed by SDS-PAGE. Iodination in the presence of amiloride inhibited incorporation but did not change the pattern of the distribution of the label among the components resolved by SDS-PAGE. Iodination of basal-lateral plasma membranes, at a yield comparable to that obtained with apical labeling, was attained after about 30 min of exposure of the intact bladder to the labeling solutions. Approximately 25% of the basal-lateral labeling was lost when the epithelial cells were harvested after collagenase treatment, implying that some iodination of the basement membrane had taken place. Less than 10% of iodination of the apical or basal-lateral surfaces was accounted for by lipid-labeling. Analysis of the labeled apical and basal-lateral species by enzymatic digestion and thin layer chromatography disclosed that virtually all the radioactivity was present as mono-iodotyrosine (MIT).

Animals↗
PubMed1979

Isolation of radio-iodinated apical and basal-lateral plasma membranes of toad bladder epithelium.

The apical and basal-lateral plasma membranes of toad bladder epithelium were radio-iodinated with the glucose-glucose oxidase-lactoperoxidase system. The covalently bound radio iodine was used as a marker during subcellular fractionation and membrane isolation. Homogenization conditions that ensured rupture of more than 80% of the cells without substantial nuclear damage were defined by Normarski optics. The nuclei were separated by differential centrifugation and the apical and basal-lateral components were resolved by differential and sucrose density gradient centrifugation. The apical components yielded two radioactive bands that were identified as glycocalyx and plasma membrane labeled with 125I. The basal-lateral components yielded a hetero-disperse pattern made up of at least 3 radioactive bands, but the bulk of the activity of ouabain-sensitive ATPase comigrated with only one of these bands. The mitochondia, identified by assays for cytochrome oxidase and NADH cytochrome c reductase activities, were separated from the radio-iodine labeled by centrifugation in sucrose density gradients under isokinetic conditions. The labeled glycocalyx and the slowly migrating components of basal-lateral labeling were separated from the radio-iodinated membranes by centrifugation at 100,000 x g x 1 hr after removal of the mitochrondria by the isokinetic method. The labeled membranes were then subjected to ultracentrifugation in sucrose density gradients under isopycnic conditions; the basal-lateral membranes containing ouabain-sensitive ATP-ase were well resolved from the apical membranes by this method. These results provide a relatively rapid method of attaining partial purification of the apical and basal-lateral plasma membranes of toad bladder epithelium.

Animals↗
PubMed1979

Molecular weight determination of commercial heparin sodium USP and its sterile solutions.

A liquid chromatographic assay for the characterization of heparin sodium USP, and heparin sterile solutions was developed. The method employs size exclusion chromatography and computer-based data collection and manipulation. An examination of commercially available heparin showed only minor differences between the heparins extracted from beef lung and porcine intestinal mucosa. The molecular weight averages of the material and its sterile solutions were 9000-12,000 daltons. A correlation was observed between average molecular weight and anticoagulant activity for the heparin sodium samples examined.

Animals↗
PubMed1978

Adenylate cyclase of human parathyroid gland.

Experiments were performed on a particulate fraction from human parathyroid glands. A high activity of adenylate cyclase was detected which was linear with time and protein concentration. The enzyme had an optimum pH in the range of 7-8 and a Km for ATP of 0.44 X 10(-3) M. Ca++ had a profound inhibitory effect; a concentration of 0.5 mM Ca++ reduced enzyme activity by 60%. Maximal enzyme activity was obtained with 5 mM Mg++; higher concentrations of this cation also inhibited enzyme activity. The effect of Mn++ was similar to that of Mg++. Enzyme activity was stimulated by NaF, catecholamines, glucagon, and calcitonin. The effect of catecholamines seems to be mediated through beta-adrenergic receptors.

Adenoma↗
PubMed1976

Duplication of aortic wall seen by echocardiography.

In four patients, echocardiography showed duplication of an aortic wall echo. An aortic dissection was present in only one. Other causes for the echocardiographic pattern were abscess in the interventricular septum, mitral stenosis, and dilatation of the noncoronary sinus of Valsalva. Division of the echo from the mitral ring into two separate posterior aortic wall echoes was seen only in the patient with dissecting aneurysm; it is suggested that this appearance adds to the specificity of the finding of aortic wall duplication by echocardiography in the diagnosis of aortic dissection.

Abscess↗
PubMed1975

Effect of aldosterone on potassium transport in the toad bladder.

The effect of aldosterone on potassium uptake by the toad bladder is described. The hormone stimulated the uptake of potassium across the serosal border of the bladder. The increased uptake was the consequence of an increase in the rate of potassium influx. An effect on potassium uptake was characterized by a latent period of approximately 60 min; it was evident for periods as long as 5 h, and it was abolished by addition of actinomycin D. The time course of the aldosterone effect on potassium closely resembled the effect of the hormone on sodium transport. It is suggested that aldosterone influences potassium transport in the toad bladder via DNA-dependent RNA synthesis. In addition, it is suggested that the effect of the hormone on potassium and sodium may be in some way related.

Aldosterone↗
PubMed1975

Natriuretic hormone.

The factors that control sodium excretion have been the subject of considerable work in recent years. The natriuresis that follows expansion of the extracellular fluid volume is mediated to a large extent by inhibition of tubular sodium reabsorption. Of the several mechanisms proposed to explain this inhibition, considerable interest has followed the suggestion that a humoral substance is released into the blood stream in response to volume expansion. The present article reviews the evidence for and against the existence of such a humoral substance (natriuretic hormone). It also discusses its proposed chemical nature and its possible site of origin in the organism as well as its mode of action.

Adrenal Glands↗
PubMed1974

Effects of acetazolamide on the urinary excretion of cyclic AMP and on the activity of renal adenyl cyclase.

Acetazolamide, an inhibitor of the enzyme carbonic anhydrase, increased the urinary excretion of cyclic AMP in normal and parathyroidectomized rats. The increase was greater in rats with intact parathyroid glands than in parathyroidectomized rats. This rise in the urinary excretion of cyclic AMP was not due to an increase in urine flow or a change in urine pH. Furosemide caused an increase in urine flow, but did not affect the excretion of cyclic AMP or phosphate. Alkalinization of the urine with bicarbonate did not increase the urinary excretion of phosphate or cyclic AMP. Acetazolamide increased the productionof cyclic AMP by rat renal cortical slices in vitro. This effect was dose-dependent. Acetazolamide also stimulated the activity of renal cortical adenyl cyclase in a dose-dependent manner but had no effect on the activity of cyclic nucleotide phosphodiesterase. The pattern of urinary excretion of cyclic AMP and phosphate after administration of acetazolamide was similar to that observed in rats given parathyroid hormone. It is suggested that acetazolamide stimulates the renal production of cyclic AMP by activating adenyl cyclase and that this may be the mechanism by which this inhibitor of carbonic anhydrase produces phosphaturia.

Acetazolamide↗