PubMed Health⌕ Search

Biomedical subjects

B Tantini

Publications and source records attributed to B Tantini.

14 recordsLinked to original sources
PubMed1992

[Variations in the functionality of cardiac adenyl cyclase as a function of age].

The metabolic and functional activity of the heart closely depends on cAMP and therefore on the integrity of adenylate cyclase (AC) system. Alterations of this signal transduction system might be co-responsible for the impairment of cardiac performance observed with aging. Evidence is here provided that basal activity of cardiac membrane-bound (48,000 x g) AC significantly declines with the age of the rat (1, 12, 24 month-old). This is accompanied with the decrease of cAMP content, which leads to the fall of cAMP/cGMP molar ratio a possible final determinant of cardiac performance. Kinetic analyses indicate that aging is associated with a net increase of the Km of a cardiac AC, while the Vmax is unaffected. Besides, the response in vitro of AC from 24-month-old heart to the inhibitor spermine or a different stimulants, such as Gpp (NH) p, isoproterenol, PGE1 or forskolin, is significantly lower than that of AC from 1 month-old one. The suggestion is made that aging causes an impairment in the capability of the catalytic moiety of cardiac AC to make functional complexes with activated guanine nucleotide binding proteins.

Adenylyl Cyclases↗
PubMed1990

Influence of docosahexaenoic acid on phosphatidylinositol metabolism in cultured cardiomyocytes.

Polyunsaturated fatty acids are involved at several steps in the turnover of phosphatidylinositol mediated by alpha 1-adrenoceptors. We have cultured neonatal rat cardiomyocytes in a medium containing docosahexaenoic acid (C22:6n3) and have investigated the effects produced by the change in the fatty acid composition of phosphatidylinositol on alpha 1-adrenoceptor-mediated phosphatidylinositol metabolism. The experimental cells, in which phosphatidylinositol was significantly enriched in docosahexaenoic acid and depleted in arachidonic acid, showed a reduced ability to incorporate labeled inositol into phospholipids in comparison with control cells, both in basal conditions and after stimulation by phenylephrine. This decreased incorporation led to a reduced availability of inositol phospholipids, substrates of phospholipase C, and to a reduced production of inositol phosphates under basal conditions.

Animals↗
PubMed1990

Effect of bacterial toxins on spermine-induced inhibition of adenylate cyclase activity of cultured heart cells.

The exposure of quiescent cultures of cardiac cells to 1 microM spermine for 2 hours leads to an increase of the content of intracellular polyamines and to a 40% decrease of basal adenylate cyclase activity. The response of adenylate cyclase to stimulation by PGE1 is reduced by about 50% after spermine treatment. The effects of the amine on adenylate cyclase are completely prevented by pretreating the cells with pertussis toxin which blocks the activation of the inhibitory guanine binding protein (Gi). In vitro experiments with adenylate cyclase from cells pre-treated with pertussis toxin show that spermine fails to reduce basal enzyme activity and to counteract the stimulation by PGE1 or forskolin. Cholera toxin, which blocks the deactivation of the stimulatory protein (Gs), does not influence the effects of spermine either in vivo or in vitro. The results suggest that spermine acts through the activation of Gi. This hypothesis is supported by the fact that, in vitro, the inhibition of stimulated adenylate cyclase by the amine is synergistic with that of a stable analog of GDP, GDP beta S, which causes deactivation of Gs.

Adenylate Cyclase Toxin↗
PubMed1988

Study on the role of endogenous polyamines in glucagon, isoproterenol or serum-mediated induction of tyrosine aminotransferase in cultured heart cells.

In confluent and serum-starved embryonic heart cell cultures, the addition of serum (10%), glucagon (GLU, 0.1 microM) or isoproterenol (ISO, 10 microM), causes the onset of ornithine decarboxylase (ODC) activity, with a maximum after 5-6 hr. This is paralleled by polyamine accumulation and by the induction of TAT, which, in the case of GLU and ISO, exhibits maximal activity at 4-3 hr respectively, followed by a net decline. Cyclic AMP (cAMP) also accumulates after exposure to GLU or ISO. However, under different conditions of ODC inhibition, serum fails to induce TAT, thus supporting a relevant role of cellular polyamines in serum action. Conversely, cAMP and TAT responses to GLU or ISO are markedly improved under prevention of polyamine accumulation, which also leads to a longer lasting TAT inducibility. The suggestion is made that polyamines are not required in the cAMP-dependent mechanism of TAT induction, but rather in the restoration of the basal activity of the enzyme.

Animals↗
PubMed1985

Reduced mechanical activity of perfused rat heart following morphine or enkephalin peptides administration.

In the isolated and perfused rat heart, the addition of morphine, methionine-enkephalin or leucine-enkephalin to the coronary perfusate, significantly reduces the mechanical activity by negatively affecting both the heart rate and the developed tension. These effects are dose dependent and maximally evident with leucine-enkephalin. Furthermore all the opioids strongly reduce the activity of isoproterenol-stimulated hearts. The suggestion is made that opioid peptides directly influence the cardiac mechanical activity possibly by interacting with membrane-receptor systems.

Animals↗
PubMed1983

Increased cyclic GMP content in confluent and serum-restricted heart cell cultures exposed to polyamines.

Cyclic AMP (cAMP) and cyclic GMP (cGMP) have been implicated as intracellular signals in the transition from a resting to a growing state. This suggestion comes from observations showing that the addition of growth promoting factors to quiescent cell cultures causes a rapid and transient decrease in cAMP and an increase in cGMP contents [9, 11] and that exogenous cAMP or cGMP congeners reduce or stimulate cell growth respectively [6, 13]. In view of this antagonistic effect elicited by the two nucleotides, it has been suggested that a fall in cAMP/cGMP ratio might be the triggering event for the initiation of cell proliferation [6]. Since polyamines correlate positively with active cell division [7], a possible involvement of these biogenic polycations in the regulation of cellular cyclic nucleotide contents is worthwhile investigating. Our previous reports have shown indeed that in different cultured cell types, spermine, spermidine and putrescine, at relatively low doses, are able to reduce cAMP content [3] by increasing cAMP-dependent phosphodiesterase activity (cAMP-PDE) [4] and to counteract the action of different cAMP-mediated effectors [3]. Besides endogenous polyamines seem to be involved in the cAMP-mediated induction of cAMP-PDE, as observed in heart cell cultures [4]. This report shows that the addition of each individual polyamine to confluent and serum-restricted heart cell cultures, while lowering cAMP content, induces an early and rapid increase of cGMP content by reducing the rate of its degradation.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1979

Polyamines and cellular adenosine 3' :5'-cyclic monophosphate.

The effect of polyamines on the cellular concentrations of cyclic AMP was studied. It was shown that 1 microM-spermine caused a decrease in cyclic AMP in chick-embryo heart cells, chick-embryo fibroblasts, neuroblastoma, glioma and neuroblastoma-glioma hybrid cells, grown in culture. A similar decrease was observed when polyamines were added to cells in the presence of a phosphodiesterase inhibitor or after stimulating the cells with various hormones. Noradrenaline was used in cultures of heart cells, prostaglandin E1 and adenosine for neuroblastoma and neuroblastoma-glioma hybrids, whereas isoproterenol was used for the stimulation of glioma cells. Polyamines at higher concentrations were either without effect or caused a slight increase in cyclic AMP. Spermidine (10 microM) also caused a decrease in cellular cyclic AMP, as did 0.1 microM-putrescine. It is suggested that the effect of polyamines on cellular cyclic AMP may be explained by the effect of these polycations on the activity of cellular phosphodiesterase.

Adenosine↗
PubMed1979

[Effect of different oxygen pressure levels on the transport of alpha-aminoisobutyric acid in myocardial cell cultures].

The activity of aminoacid transport, as measured by alpha-aminoisobutyrate uptake, has been studied in confluent myocardial cell cultures exposed to different oxygen tensions. The results obtained indicate that the rate of cellular uptake and accumulation of the inert aminoacid increase with time as the fraction of oxygen is reduced. When alpha-aminoisobutyrate was added in presence of all other aminoacids of the medium, the effect of oxygen was also evident, suggesting a mechanism which overcomes the competitive action of the other aminoacids assigned to the same transport system of alpha-aminoisobutyrate (A system). The modulation of aminoacid transport activity may represent one of the possible mechanisms by which environmental oxygen affect the rate of cellular protein synthesis.

Aminoisobutyric Acids↗