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P Belluco

Publications and source records attributed to P Belluco.

10 recordsLinked to original sources
PubMed1993

A pharmacological, crystallographic, and quantum chemical study of new inotropic agents.

The cardiac activity of a series of milrinone analogues, 2-substituted 3-acyl-1,6-dihydro-6-oxo-5-pyridinecarbonitriles, 1,6,3,2,11,12-hexahydro-6,3-dioxo-5-quinolinecarbonitriles, the correlated carboxylic acids, 2-substituted 3-acyl-6(1H)-pyridones, and 7,8-dihydro-2,5(1H,6H)-quinolinediones, was evaluated in spontaneously beating and in electrically driven atria from reserpine-treated guinea pigs. Their effects were compared with those induced by amrinone and milrinone in both the atria preparations. Compounds SF28 (3-acetyl-1,6-dihydro-2-methyl-6-oxo-5-pyridinecarbonitrile) and SF40 (7,8-dihydro-7-methyl-2,5(1H,6H)-quinolinedione) were the most effective positive inotropic agents. An inhibition of the negative influence exerted by endogenous adenosine on heart preparations seems to be involved in their contractile activity. SF38 (3-benzoyl-2-phenyl-6(1H)-pyridinone), on the contrary, reduced the contractile force and the frequency rate of guinea pig atria with a mechanism not related to an activation of cholinergic or purinergic inhibitory receptors on the heart. X-ray analysis carried out on the three model compounds, SF28, SF40 (positive inotropic agents), and SF38 (negative inotropic agent), and molecular modeling evidenced that the change from phenyl (SF38) to methyl (SF28) or the introduction of a side cyclic aliphatic chain (SF40) results in a variation of conformational preference and topography which may address the different molecules toward distinct receptor pockets according to the resulting inotropic effect.

Amrinone↗
PubMed1992

Antagonism towards endogenous adenosine and inhibition of cGI-PDE in the cardiac effects of amrinone, milrinone and related analogues.

1. The effect of amrinone, milrinone and of three milrinone analogues was tested on spontaneous chronotropic and inotropic activity of guinea-pig isolated atria, on the activity of cGMP-inhibited phosphodiesterase (cGI-PDE) from guinea-pig heart and on specific binding of N6-cyclohexyl[3H]adenosine ([3H]CHA) to Ri adenosine receptors in guinea-pig atria. 2. The Ki-values towards [3H]CHA binding to Ri receptors were linearly related to the EC50S for the increase in force of contraction but not to the EC50S for the increase in frequency of the atria. The Ki values towards cGI-PDE were linearly related to the EC50S for the positive chronotropic effect.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1992

Synthesis and cardiotonic activity of 2-substituted 5-cyano-1,6-dihydro-6-oxo-3-pyridinecarboxylic acids and their methyl or ethyl esters.

The synthesis of ethyl or methyl esters of 5-cyano-1,6-dihydro-6-oxo-3- pyridinecarboxylic acids carrying as 2-substituent a polar group such as CO2C2H5, (CH2)2CO2CH3, (CH2)3CO2C2H5, CH2OCH3, or CF3 group is described. Also 2-[5-cyano-1,6-dihydro-2-(1,1-dimethylethyl)-6-oxo-3-pyridyl]-2- oxoacetic acid and 2,5,6,8-tetrahydro-2,5-dioxo-1H-thiopyrano[3,4-b]pyridine-3-carbon itrile were prepared. Nearly all the above esters gave routinely the corresponding carboxylic acids by alkaline hydrolysis followed by acidification. As milrinone analogues, the above compounds were tested on contractile activity and frequency rate of spontaneously beating atria from reserpine-treated guinea-pigs. 5-Cyano-2-trifluoromethyl-1,6- dihydro-6-oxo-3-pyridinecarboxylic acid and, in a lesser degree, the relative ethyl ester showed an appreciable positive inotropic activity, although inferior to that of milrinone.

Animals↗
PubMed1991

An analysis of the mechanism of the inotropic action of some milrinone analogues in guinea-pig isolated atria.

1. It has been reported previously that the milrinone analogues, ethyl 5-cyano-1,6-dihydro-2-methyl-6-oxo-3 pyridine carboxylate (I) and ethyl 5-cyano-1,6-dihydro-2-ethyl-6-oxo-3 pyridine carboxylate (II) exert a positive inotropic effect (EC50 = 15.6 +/- 0.2 microM and 40.3 +/- 0.1 microM) both on spontaneously beating and on electrically driven atria from reserpine-treated guinea-pigs. In the present study the mechanism of the inotropic action of these two agents was investigated. 2. In electrically driven left atrium from reserpine-treated guinea-pigs the EC50 values for inotropic activity for compounds (I) and (II) corresponded to that of milrinone (EC50 = 25 +/- 0.1 microM) but compound (I) induced a greater maximum effect. This corresponded to a percentage increase in developed tension over control of 63 +/- 0.3 whereas the maximum inotropic effect of milrinone was 48 +/- 0.3 and that of compound (II) was 47 +/- 0.2. 3. The inotropic activity of compounds (I) and (II) (10-100 microM) was resistant to propranolol (0.1 microM), thus excluding the involvement of beta-adrenoceptors. 4. Since the inotropism induced by compounds (I) and (II) was not reduced by carbachol (1 nM-0.5 microM), an action involving changes in adenosine 3':5'-cyclic monophosphate (cyclic AMP) can be excluded. 5. The inotropic action of compounds (I) and (II) was blocked selectively by 8-phenyltheophyline (10 microM) or adenosine deaminase (2 u ml-1). 6. Both (I) and (II) inhibited, in an apparently competitive manner, the negative inotropic effect induced by N6-(L-phenylisopropyl) adenosine (L-PIA), a stable adenosine agonist. The pA2 values for (I) and (II) were 4.79 and 4.36, respectively.7. In rat brain compounds (I) and (II) inhibited the specific binding of N6-cyclohexyl[3H]-adenosine- ([3H]-CHA) with an IC50 of 0.18 + 0.01 mM and 0.25 + 0.02 mm, respectively, which were similar to their IC50 values for blocking the PIA-induced negative inotropic effect and which are also in the range of concentrations that are effective in inducing positive inotropism in guinea-pig atria.8. The results from the present study suggest that antagonism of endogenous purines causes positive inotropism without affecting intracellular cyclic AMP levels.

Adenosine↗
PubMed1990

Different action of milrinone analogs in guinea-pig atria.

1. Three new milrinone analogs, esters of 2-substituted 5-cyano-1,6-dihydro-6-oxo-3-pyridine carboxylic acids [compounds I, II and III] displaced 3H-CHA (N6-cyclohexyl[3H]-adenosine) from its binding sites to Ri receptors in the rat brain. 2. When tested on the contractile activity of electrically driven left atrium from reserpine-treated guinea-pigs, I induced marked positive inotropic activity, whereas the most lipophilic compounds II and III, induced negative inotropic effects. 3. These results suggest that the positive inotropic agent may act by displacing endogenous adenosine from its Ri inhibitory receptors in the atria, whereas the negative inotropic agents may act as agonists at the same adenosine receptor.

Adenosine↗
PubMedDate not supplied

Vasodilatory activity of etozoline in rat and guinea-pig isolated aorta: study of the mechanism of action.

In isolated rings of guinea-pig aorta not responding to acetylcholine, the diuretic etozoline did not influence basal vascular tone but inhibited noradrenaline- and histamine-induced contractions. The inhibition was evident at concentrations of the diuretic (10 microM-1 mM) suitable to inhibit, in a competitive manner, the contractions evoked by a K+ channel blocker, tetraethylammonium, in the same preparation (Dorigo et al., 1989, 1990). In isolated rings of guinea-pig aorta, etozoline, at very low concentrations (1 nM-0.1 microM), inhibited also serotinin-induced contractions. The contractile effect of serotonin was abolished by nifedipine associated with 2-nitro-4-carboxyphenyl N,N-diphenyl-carbamate (an inhibitor of phospholipase C) or with etozoline, thus suggesting that the diuretic, besides inhibiting extracellular Ca++ uptake, also prevents intracellular Ca++ mobilization mediated by inositol triphosphate. In isolated rings of rat aorta responding to acetylcholine, etozoline did not influence basal vascular tone either in the absence or in the presence of superoxide-dismutase. In the same preparation, the diuretic inhibited vascular contractions induced by the three spasmogenic agents used, i.e. noradrenaline, histamine and serotonin. This inhibition occurred at concentrations of etozoline ranging from 10 microM to 1 mM and was uninfluenced by indomethacin (10 microMs). In isolated rings of rat aorta, the contractile effect of noradrenaline was not influenced by the addition of either 100 microM pyrogallol, or 10 microM methylene blue or 100 U/ml superoxide-dismutase, while the contractile responses to histamine and to serotonin were potentiated by pyrogallol and by methylene blue and reduced by superoxide-dismutase. This indicates that, in rat aorta, noradrenaline evokes only a direct contractile response, whereas both serotonin and histamine have a double effect: direct contraction of vascular smooth muscle and release of a relaxing factor from the endothelium. The inhibitory activity of etozoline towards serotonin- and histamine-induced contractions was reduced by pyrogallol and by methylene blue, whereas it was potentiated by superoxide-dismutase. The ability of etozoline to reverse the noradrenaline-induced contraction was unaffected by pyrogallol, methylene blue or superoxide-dismutase. These results emphasize the spasmolytic activity of etozoline, which seems to involve only the muscular component of rat and guinea-pig aorta.

Acetylcholine↗
PubMedDate not supplied

Mechanism of the vasodilating action of etozoline and its metabolites in guinea-pig aorta.

The mechanism of the vasodilating action of the diuretic etozoline and of its metabolites d- and l-ozolinone was studied in isolated aortic strips from reserpine-treated guinea-pigs. Etozoline (10 microM to 1 mM) induced a concentration-dependent inhibition of the contraction evoked by increasing K+ concentrations (15 to 45 mM) in the perfusion medium. The inhibition was of a noncompetitive type. Etozoline also inhibited contractions induced by increasing Ca++ concentrations in the perfusion medium of aortic strips depolarized by 40 mM K+. The inhibition was concentration-dependent and of a noncompetitive type. Tetraethylammonium, at concentrations reported to increase Ca++ influx into smooth muscle cells by closing K+ channels, induced contractions of aortic strips that were highly sensitive to inhibition by etozoline. Analysis of the concentration-response curves for tetraethylammonium showed that the antagonism by etozoline was of a competitive type. The pA2 value for etozoline was 5.01 +/- 0.16. Also arterial spasm, obtained by prolonging the exposure of vascular strips to tetraethylammonium (30 min), was completely suppressed by etozoline. l- and d-Ozolinone antagonized tetraethylammonium-induced contractions of aortic strips in an apparently competitive manner, but only at very high concentrations (1 and 3 mM, respectively). These results suggest that the vasodilating action of etozoline and of its metabolites is mediated by an inhibition of Ca++ influx into smooth muscle cells following a specific opening of K+ channels, but only etozoline may act through this mechanism at concentrations likely to be operative in vivo.

Animals↗