Federico Bennardini

Effect of ICV taurine on the impairment of learning, convulsions and death caused by hypoxia.

The effect of the intracerebroventricular (ICV) administration of taurine on amnesia, convulsions and death caused by hypoxia was investigated in mice. Taurine in doses of 80–100 μg/mouse impaired acquisition of a single trial in passive avoidance performance, but protected mice from the learning impairment induced by hypoxia. Neither β-alanine nor saccarose were able to mimic the effects of taurine. Taurine had no effect on amnesia induced by scopolamine injected intraperitoneally. Taurine protected against the onset of convulsions induced by hypoxia, while convulsions induced by pentylenetetrazole (PTZ) and hyperbaric oxygen were unaffected. The survival time of mice exposed to hypoxia was significantly increased by taurine treatment. These data suggest that taurine may play a role as an antihypoxic agent.

Inotropic effect of taurine in guinea-pig ventricular strips

At 0.9 mM CaCl2 taurine prevented the negative inotropic effect due to low calcium concentration in guinea-pig ventricular strips but not in rat strips. This taurine effect was dose-dependent. The presence (in the perfusion medium) of beta-alanine, an inhibitor of taurine transport, antagonized the effect of taurine suggesting that the action of taurine was correlated to its transport. Neither propranolol, cimetidine nor indomethacin affected the response to taurine in guinea-pig ventricular strips.

[3H]-nitrendipine binding in membranes obtained from hypoxic and reoxygenated heart

We compared the binding properties of [3H]-nitrendipine in heart membranes from normal guinea-pig heart and from hypoxic or hypoxic and reoxygenated heart. The [3H]-nitrendipine binds a single class of high capacity (Bmax 667.2 +/- 105.2) with high affinity (KD 0.14 +/- 0.02) binding sites. By contrast, in membranes of hypoxic and reoxygenated heart the Bmax decreases significantly while it remains unaffected during hypoxia. Xanthinoxidase activity is increased in hypoxic-reoxygenated hearts.

Uptake of [3H]taurine into myocardial membranes

Abstract In the ventricular sarcolemma of guinea-pig heart two uptake systems are present, a high affinity and a low affinity one. The uptake is Na − , K + , Mg 2+ dependent and Ca 2+ independent. In the absence of Mg 2+ only one uptake system is present. β-alanine, hypotaurine, homotaurine and guani-dethylsulphonate inhibit the uptake of [ 3 H]taurine; isethionic acid increases it.

Functional and binding evidence of taurine inhibition of α-adrenoceptor effects on guinea-pig ventricle

The effect of taurine on alpha- and beta-mediated positive inotropic effects was investigated in guinea-pig ventricular strips. Loading with taurine dose-dependently antagonized the phenylephrine-induced positive inotropic effect while it was ineffective on beta-mediated positive inotropic effect. The superfusion with a taurine-free medium determined a loss of intracellular taurine, while the loading with 20 mM taurine prevented this depletion. Preincubation of cardiac membranes with different concentrations of taurine (1 to 20 mM) decreased 3H-prazosin binding, and the saturation curve obtained after preincubation of cardiac membranes with 20 mM taurine showed that taurine had a more marked effect on the number of binding sites. In both experimental models, beta-alanine did not mimic any taurine effects, suggesting that taurine actions might be specific.

Positive inotropic effect of some taurine-related compounds on guinea-pig ventricular strips perfused with low calcium medium

Taurine exerts a positive inotropic effect at a low calcium concentration. Of the compounds chemically related to taurine only L-cysteic and 2-aminobenzenesulfonic acid mimic taurine action. Their effect is concentration-dependent and not linked to the restoration of taurine tissue concentration in guinea-pig ventricular strips. Our data demonstrate that: (1) carbon chain length between amino and sulfonic groups is a crucial factor in the development of activity. (2) Substitution of the sulfonic group with other acid functions such as the substitution of the primary amino group or the introduction of the -COOH group onto the beta-carbon brings about a lack of activity.

On the presence of H1-receptors in various sections of guinea-pig heart: a correlation between binding and functional studies.

The binding of3H-mepyramine in different sections of guinea-pig heart was examined.3H-mepyramine binds to a single class of binding sites to guinea-pig ventricular membranes and to right atrial suspension with an apparent dissociation constant (Kd) of 4.35 nM and 14.90 nM respectively. When treated as those obtained from the right atrium, the left atrial suspensions do not seem to bind3H-mepyramine specifically.

Taurine uptake in sarcolemma vesicles isolated from hypertrophic guinea-pig hearts

Abstract Taurine uptake by guinea-pig hypertrophie heart sarcolemma vesicles was sodium-dependent and kinetic analysis suggested the presence of only one uptake system. The apparent k m and v max were the following; 2.5 x 10 6 M and 0.43 pmoles-mg −1 protein. mi −1 respectively. The uptake was specific and was inhibited by all analogues tested, except isethionic acid. The uptake was also inhibited by NaF.

Cardiac hypoxia and subsequent reoxygenation: sensitivity to L-arginine methylester

1 The effect of L‐arginine methylester (L‐Arg‐Me) was studied in the isolated heart of the guinea‐pig perfused with hypoxic substrate‐free medium for 30 min and subsequently reoxygenated with normal saline solution for 30 min. 2 The administration of L‐Arg‐Me in basal conditions decreases dose‐dependently heart rate without any changes in the myocardial structure. 3 On the other hand, the administration of L‐Arg‐Me (5–10 mm) decreases ventricular arrhythmias, especially during reoxygenation; in fact ventricular fibrillation is abolished. 4 L‐Arg‐Me treatment increases the recovery of normal electrical and mechanical activity at the end of reoxygenation and reduces the increase in basal tone. 5 Treatment with 10 mm L‐Arg‐Me decreases lactate dehydrogenase (LDH) release in the effluent and lysosomal fragility in cardiac tissue, while it does not influence calcium gain. 6 L‐Arginine (L‐Arg) does not mimic any of the effects of L‐Arg‐Me.

Effect of Taurine on Chloride Conductance and Excitability of Rat Skeletal Muscle Fibers

Taurine is found in mammalian skeletal muscle fibers and all other excitable tissues (17), but its function is not well understood (16). Abnormal taurine contents whether pathologically or experimentally induced are often associated with changes of excitability in heart (9), nerve (8,21), and retina (4). The taurine content is increased in skeletal muscle from the dystrophic chicken (23).