Biomedical subjects

N Hernando

Publications and source records attributed to N Hernando.

40 records · Page 3Linked to original sources

PubMed1985

Lack of effect of synthetic atrial natriuretic factor on rubidium uptake by human erythrocytes.

The effect of synthetic atrial natriuretic factor on the ouabain-sensitive and the furosemide-sensitive rubidium uptake by human erythrocytes has been studied. This peptide with potent diuretic and natriuretic effects did not affect any rubidium uptake system at concentrations of 10(-7) and 10(-9) M. These results do not support that the natriuretic effect is based on the inhibition of active transport systems in the renal tubules.

Atrial Natriuretic Factor↗

PubMed1985

Lack of effect of indomethacin on systemic and splanchnic haemodynamics in portal hypertensive rats.

Portal hypertension was produced experimentally in rats by partial constriction of the portal vein. Twelve rats were injected daily with indomethacin, 4 mg/kg body weight, and 12 with the vehicle (80% ethanol, 0.5 ml/day). There were no differences in portal-systemic shunts nor systemic or splanchnic haemodynamics between indomethacin-treated and untreated rats. These results suggest that cyclo-oxygenase products do not play a significative role in haemodynamic alterations shown by portal-ligated rats.

6-Ketoprostaglandin F1 alpha↗

PubMedDate not supplied

Molecular mechanisms in proximal tubular and small intestinal phosphate reabsorption (plenary lecture).

Renal and small intestinal (re-)absorption contribute to overall phosphate(Pi)-homeostasis. In both epithelia, apical sodium (Na+)/Pi-cotransport across the luminal (brush border) membrane is rate limiting and the target for physiological/pathophysiological alterations. Three different Na/Pi-cotransporters have been identified: (i) type I cotransporter(s)--present in the proximal tubule--also show anion channel function and may play a role in secretion of organic anions; in the brain, it may serve vesicular glutamate uptake functions; (ii) type II cotransporter(s) seem to serve rather specific epithelial functions; in the renal proximal tubule (type Ila) and in the small intestine (type IIb), isoform determines Na+-dependent transcellular Pi-movements; (iii) type III cotransporters are expressed in many different cells/tissues where they could serve housekeeping functions. In the small intestine, alterations in Pi-absorption and, thus, apical expression of IIb protein are mostly in response to longer term (days) situations (altered Pi-intake, levels of 1.25 (OH2) vitamin D3, growth, etc), whereas in renal proximal tubule, in addition, hormonal effects (e.g. Parathyroid Hormone, PTH) acutely control (minutes/hours) the expression of the IIa cotransporter. The type II Na/Pi-cotransporters operate (as functional monomers) in a 3 Na+:1 Pi stoichiometry, including transfer of negatively charged (-1) empty carriers and electroneutral transfers of partially loaded carriers (1 Na+, slippage) and of the fully loaded carriers (3 Na+, 1 Pi). By a chimera (IIa/IIb) approach, and by site-directed mutagenesis (including cysteine-scanning), specific sequences have been identified contributing to either apical expression, PTH-induced membrane retrieval, Na+-interaction or specific pH-dependence of the IIa and IIIb cotransporters. For the COOH-terminal tail of the IIa Na/Pi-cotransporter, several interacting PDZ-domain proteins have been identified which may contribute to either its apical expression (NaPi-Cap1) or to its subapical/lysosomal traffic (NaPi-Cap2).

Absorption↗

PubMedDate not supplied

Molecular characteristics of phosphate transporters and their regulation.

A key process in overall P(i)-homeostasis is renal proximal tubular reabsorption of inorganic phosphate (P(i)), which involves secondary active sodium/phosphate (Na(+)/P(i)) cotransport reabsorption at the brush border membrane. Among the two different molecularly identified Na(+)/P(i) cotransporters, the type-IIa Na(+)/P(i) cotransporter (NaPi-IIa) accounts for up to 70% of brush border membrane transport. Regulation of renal P(i) reabsorption centers around brush border membrane insertion and retrieval of transporter protein under the influence of hormonal and nonhormonal factors. Immunohistochemical and fluorescence techniques have provided new insights into the tissue distribution and the regulation processes. The intrinsic electrogenicity of NaPi-IIa, has allowed detailed studies of the transport kinetics of NaPi-IIa and, combined with mutagenesis methods, structure-function information at the protein level is emerging.

Amino Acid Sequence↗