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F Favilli

Publications and source records attributed to F Favilli.

At least 37 records · Page 2Linked to original sources
PubMed1990

Changes in metabolite transport by small intestine and kidney of young and old rats.

We have studied the influence of the ageing phenomenon on metabolite absorption by the small intestine and the kidney of the rat, using isolated brush-border membrane vesicles prepared from 2 groups, one composed of 2 month, and the other of 24 month, animals. "Overshoot", which is typical of Na(+)-glucose cotransporter activity, disappeared in the duodenum and decreased in the kidney of the old rats. Short-circuiting of vesicles with valinomycin showed that, in the presence of K+ and valinomycin, "overshoot" decreased in both groups by about the same percentage. The Na(+)-dependent uptake of aspartate and phenylalanine showed contrasting pictures in the jejunum and kidney of the aged animals: aspartate transport decreased only in the kidney, while phenylalanine uptake was negatively affected in the jejunum. Na(+)-dependent citrate uptake, studied in renal brush-border membrane vesicles, was lower in the old rats. The Km values determined for Na(+)-dependent D-glucose and citrate uptake in the kidney did not meaningfully differ between the two groups. A continuous decrease in Na(+)-dependent D-glucose and citrate uptake in the rat kidney, during ageing, was demonstrated.

Aging↗
PubMed1989

Glutathione transport across intestinal brush-border membranes: effects of ions, pH, delta psi, and inhibitors.

We characterized glutathione transport in brush-border membrane vesicles (BBMV) that were prepared from rabbit small intestine in which gamma-glutamyl transpeptidases (gamma-glutamyltransferases, EC 2.3.2.2) had been inactivated by a specific affinity-labeling reagent (AT125). Intact GSH transport was strongly increased by the presence of Na+, K+, LI+, Ca2+ and Mn2+ and, of all these, the Ca2+ activation effect was prevalent. This cation effect was selective and catalytic but not energetic; Vmax obtained in the presence of both Na+ and Ca2+ was about 6-times higher than it was in their absence, while Km did not change. Moreover, these cations almost completely eliminated GSH binding on the membrane surface. Na+ activation cannot be explained as a stimulation effect on the Na+-H+ antiport system, since a GSH proton-driven transport was excluded. We determined a pH optimum (7.5), while low or high extravesicular pH values diminished the GSH uptake rate. The Ca2+ effect on GSH transport, when an electrical potential difference was imposed across BBMV, was different from that of monovalent cations. Indeed, experiments performed by valinomycin-induced K+ diffusion potential or by anion substitution showed that the GSH transport system was an electroneutral process in the presence of Na+ or K+, but that it was electrogenic in the presence of Ca2+ or in the absence of extravesicular cations. These results suggest that GSH is also cotransported with these cations, without its accumulation inside vesicles. Moreover, since GSH is negatively charged, the effect of pH changes and of cation activation on GSH transport is arguably mediated by changes in the ionization state of certain groups as the carrier site and of GSH itself, indicating the electrostatic nature of GSH binding sites on the transporter. The high Ca2+ activation effect is perhaps also partly due to fluidity changes in the lipoproteic microenvironment of the GSH transporter. Moreover, this transport system has high affinity with GSH, given the low Km value (17 microM) and the fact that it was only inhibited by GSH S-derivatives and by GSH monoethyl ester, which probably share the same transport system.

Animals↗
PubMed1989

Glucose transport during ageing by human intestinal brush-border membrane vesicles.

Glucose absorption by the small intestine is a complex phenomenon, that can be successfully studied by means of isolated brush-border and basolateral membrane vesicles of the enterocytes. We have carried out transport experiments on isolated brush-border membrane vesicles from the human small intestine, taking into account the age of the subjects. Our studies demonstrated that Na+-glucose cotransporter activity decreased as age increased with the "overshoot" phenomenon disappearing altogether in the oldest subjects. This effect was compared to that observed in intestinal membrane vesicles of young patients suffering from Crohn's disease; in this case there was a marked decrease in the Na+-dependent D-glucose uptake, but the "overshoot", even though low, was present. K+-dependent D-glucose transport, diffusion of L-glucose and the levels of some enzyme markers for intestinal brush-border membranes were also studied.

Adult↗
PubMed1988

Glutathione-mediated transport across intestinal brush-border membranes.

Glutathione transport was studied in brush-border membrane vesicles of rabbit small intestine in which gamma-glutamyl transpeptidase (EC 2.3.2.2) had been inactivated by a specific affinity-labeling reagent, L-(alpha S,5S)-alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid (AT125). Transport of intact [glycine-2-3H]GSH occurred into an osmotically active intravesicular space of AT125-treated membranes. The 0.1 M NaSCN gradient (Na+ inside greater than Na+ outside) in the transport medium could be replaced with KSCN or NaCl without affecting transport activity. The initial rate of GSH transport followed Michaelis-Menten saturation kinetics (Km = 17 microM). The results suggest that, in these membranes, there was an Na+-independent mediated transport for intact GSH with marked specificity and affinity. In fact glycine, glutamic acid and cysteine did not decrease GSH uptake, as was also true for glycylglycine and glycylglycylglycine; only gamma-glutamylcysteinylglycyl ester, a derivative of GSH, partially inhibited GSH transport.

Animals↗
PubMed1988

[Effect of natural or synthetic detergents on the transport of D-glucose in the membranes of vesicles of the brush border of the intestine of the rabbit].

We describe here the effects of natural and synthetic detergents on the D-glucose transport into brush-border membranes of vesicles of rabbit's intestine. Two synthetic detergents: Triton X-100 and dodecyltrimethylammonium bromide have been found very strong inhibitors (more than 50 p. 100 of inhibition of maximal D-glucose uptake). Kinetic studies showed that these detergents behaved as mixed type inhibitors. The Na+-dependent transport of amino acids (aspartic acid, lysine, phenylalanine) is only poorly affected by dodecyltrimethylammonium bromide, while Triton X-100 inhibits unspecifically all the transport studied.

Animals↗
PubMed1988

Effect of 25-hydroxyvitamin D3 on Na+-dependent D-glucose transport in rachitic rats.

We have previously reported that feeding rats on Steenbock and Black's rickets-inducing diet, deficient in vitamin D and with an altered Ca/P ratio, leads to metabolic consequences and a marked decrease of Na+-dependent D-glucose uptake at the jejunum-ileum level. To clarify the relationship between experimental rickets and D-glucose uptake, 25-hydroxyvitamin D3 (25-OH-D3) was given to rats fed on the rickets inducing diet. In the jejunum-ileum of these animals Na+-dependent D-glucose uptake returned to the values of the controls while the decrease in D-glucose uptake in the brush-border membrane vesicles prepared from kidney cortex of rachitic animals was not corrected by the administration of 25-OH-D3.

Animals↗
PubMed1987

1-O-n-octyl-beta-D-glucopyranoside as a competitive inhibitor of Na+-dependent D-glucose cotransporter in the small intestine brush-border membrane.

1-O-n-Octyl-beta-D-glucopyranoside is a competitive inhibitor of the Na+-dependent D-glucose uptake into rabbit, rat and human intestinal brush-border membrane vesicles. The lack of effect on the equilibrium uptake demonstrates that the detergent does not act by rupturing the vesicles; no membrane leakiness was apparent at the concentrations of octylglucopyranoside used, since D-glucose uptake is not inhibited even in the absence of the Na+ gradient (in K+ solution). There is a competitive interaction between octylglucopyranoside and D-glucose, as shown by Dixon and by Hunter and Down plots. The selectivity of the detergent effect is confirmed by its modest influence on amino acid uptake.

Amino Acids↗
PubMed1987

D-glucose uptake in intestinal brush-border membrane vesicles of rachitic rats.

We have previously reported the metabolic consequences of feeding rats Steenbock and Black's rickets-inducing diet, deficient in vitamin D and with an altered Ca/P ratio. Using isolated brush-border membrane vesicles prepared from the jejunum, ileum and duodenum of control and rachitic rats, we have demonstrated a marked decrease of Na+-dependent D-glucose uptake at jejunum-ileum level of rachitic rats. At duodenum level Na+-dependent D-glucose transport was not influenced by rickets. A lack of any significant difference between the two animal groups was observed studying the facilitated transport of D-glucose, the diffusion of L-glucose and the Na+-dependent uptake of phenylalanine and aspartate.

Animals↗
PubMed1985

[Anionic detergents, natural and synthetic, as selective denaturants of various dehydrogenases].

The effects of natural (fatty acids) or synthetic detergents on some highly purified enzymes has been studied. Four dehydrogenases (glucose-6-phosphate-, lactico-, malico- and isocitrico-dehydrogenase) are highly inhibited by these products. Other enzymes are not inhibited or inactivated by them. The mechanism of the action of detergents is specifically based on their binding to the enzyme at the level of its proteic constituent and close to its active group.

Animals↗
PubMed1985

Detergents as selective inhibitors and inactivators of enzymes.

In order to study the detergent-enzyme interaction and to clarify whether such an interaction produces specific or non-specific effects, we investigated the action of natural and synthetic detergents on enzymatic systems of different levels of complexity (crystalline enzymes, crude homogenates, organ preparations, organisms in toto i.e. rats and germinating seeds). The enzyme-detergent interaction was examined both as a time-independent phenomenon (inhibition) and as a time-dependent phenomenon (inactivation). In in vitro experiments a clear inhibition of pyridine-dependent dehydrogenases by long-chain anionic detergents was found. Cationic detergents have their greatest effect on lipase, LDH, MDH and ICDH from rat liver homogenates. At low concentrations SDS inactivates all the dehydrogenase enzymes studied. With high concentrations (10 mM) of SDS and dodecyltrimethylammonium bromide (C12), there was a sharp and non-specific decrease of enzymatic activities. In the in vivo studies, rats were given detergents to drink; the cationic detergent (C12) was far more effective than SDS with enzymes from both intestine and liver homogenates. SDS and C12 do not seem to interfere with enzyme activities at the beginning of the germination of Pinus pinea and Triticum durum seeds. However a marked reduction of activities does occur at the respective maximum germination times of these seeds. The nonionic detergent is ineffective both as inhibitor and as inactivator.

Alcohol Dehydrogenase↗
PubMed1984

On the interaction between synthetic detergents and enzymatic proteins.

Eight highly purified and crystalline enzymes representative of fundamental metabolic pathways and of cellular structure were tested with seven detergents. The enzyme-detergent interaction was studied as a time-independent (inhibition) or time-dependent (inactivation) phenomenon. Our results imply a specificity of detergent action on the enzymes studied.

Alanine Transaminase↗
PubMed1984

[Interaction : detergents-enzymes].

The study on the action of eight synthetic detergents of various types of well defined structure and properties (neutral, anionic, cationic) has been realized on fourteen highly purified enzymes of animal or vegetal origin of great metabolic importance, on these of homogenates of intestine or liver of normal rats and of rats fed during a relatively long period with food containing synthetic detergents. The action of all studied detergents on highly purified enzymes has been characterized as this of specific effectors, producing a reversible denaturation of enzymatic proteins to whom they combine. Ingestion of detergents by rats leads, probably by the same mechanism, to a diminution in vivo of the activity of some intestinal and hepatic enzymes.

Animals↗
PubMed1983

The palmitoleate: a natural selective denaturant of enzymes.

A study has been carried out in order to explain the enzyme-palmitoleate interaction. The highly purified and crystalline enzymes representative of fundamental metabolic pathways were: alcohol dehydrogenase (ADH), lactate dehydrogenase (LDH), malate dehydrogenase (MDH), isocitrate dehydrogenase (ICDH), glucose-6-phosphate dehydrogenase (G6P-DH), alkaline phosphatase. The enzyme-palmitoleate interaction was studied as a phenomenon time-independent (inhibition) and time-dependent (inactivation). Palmitoleate inhibited remarkably LDH, MDH, ICDH and G6P-DH. A kinetic analysis of the inhibitory action of palmitoleate on LDH and MDH was also carried out. Inactivation studies have shown that ADH and alkaline phosphatase are not sensitive to palmitoleate action, unlike the other enzymes. A comparison was made between the action of palmitoleate and that of a synthetic anionic detergent, sodium dodecyl sulfate (SDS).

Alcohol Dehydrogenase↗
PubMed1982

Specific interaction among some enzymes and sodium dodecyl sulfate.

The effect of 1-butanesulfonic acid sodium salt and sodium dodecyl sulfate on the activity of highly purified and crystalline enzymes with marked differences in structure and function has been studied. The enzymes were: alcohol dehydrogenase; lactate dehydrogenase; malate dehydrogenase; isocitrate dehydrogenase; glucose-6-phosphate dehydrogenase; lipase; alkaline phosphatase. While 1-butanesulfonic acid sodium salt, at the studied concentrations, resulted generally inactive, sodium dedecyl sulfate showed a selective inhibitory effect, always under the critical micellar concentration. A kinetic analysis of the inhibitory action was also carried out.

Alkaline Phosphatase↗
PubMed1982

[Sodium dodecyl sulfate, concurrent inhibitor of several dehydrogenases].

The effect of sodium dodecyl sulfate on the activity of highly purified or crystalline enzymes has been studied. The enzymes were: lactate dehydrogenase (LDH), malate dehydrogenase (MDH). isocitrate dehydrogenase (ICDH), glucose-6-phosphate dehydrogenase (G6P-DH), lipase, alkaline phosphatase. Sodium dodecyl sulfate, always under the critical micellar concentration, shows a selective inhibitory effect. A kinetic analysis of the inhibitory action on LDH, MDH, ICDH and G6P-DH was also carried out.

Alkaline Phosphatase↗
PubMed1978

Some properties of glucose-6-phosphate dehydrogenase from rat and chick brain: a comparative study.

1. Glucose-6-phosphate dehydrogenase (G6PDH) has been purified to homogeneity from rat and chick brain by affinity chromatography with Sepharose bound 2',5' ADP. 2. Some properties of the two enzymes are studied and the effects of hydrogen ion concentration, Mg2+ ions, temperature and urea on the initial rate of enzyme are described. 3. G6PDH from chick brain differs from the rat enzyme in affinity for 2',5' ADP Sepharose, in pH optimum, in heat stability and it is differently affected by Mg2+ ions. No effect is detectable after urea treatment on enzymes from both sources.

Animals↗