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S Salomone

Publications and source records attributed to S Salomone.

29 records · Page 2Linked to original sources
PubMed1995

Effects of 8-bromo cyclic GMP and verapamil on depolarization-evoked Ca2+ signal and contraction in rat aorta.

1. The pharmacological action of NO donors is usually attributed to a cellular rise in guanosine 3':5'-cyclic monophosphate (cyclic GMP), but this hypothesis is based only on indirect evidence. Therefore, we have studied the effects of cyclic GMP on Ca2+ movements and contraction in rat isolated endothelium-denuded aorta stimulated by KCl depolarizing solution using the permeant analogue 8-bromo cyclic GMP (BrcGMP). Isometric contraction and fura-2 Ca2+ signals were measured simultaneously in preparations treated with BrcGMP and with verapamil. The activation of calcium channels was estimated by measuring the quenching rate of the intracellular fura-2 signal by Mn2+ and by the depolarization-dependent influx of 45Ca2+. 2. Stimulation with 67 mM KCl-solution evoked an increase in cytosolic Ca2+ concentration ([Ca2+]cyt) and a contractile response which were inhibited by pretreatment with verapamil (0.1 microM) or BrcGMP (0.1-1 mM). However, the inhibition of the fura-2 Ca2+ signal was significantly higher with verapamil than with BrcGMP, whereas the contraction was inhibited to a similar extent. 3. When preparations were exposed to K(+)-depolarizing solution in which the calcium concentration was cumulatively increased, the related increase in fura-2 Ca2+ signal was barely affected by BrcGMP, whereas the contractile tension was strongly and significantly inhibited. 4. Cellular Ca2+ changes were also estimated with 45Ca2+. 45Ca2+ influx in resting preparations was significantly reduced by BrcGMP (0.1 mM) but not by verapamil (0.1 microM); 45Ca2+ influx in KCl-depolarized preparations was reduced by verapamil but was unaffected by BrcGMP. 5. Measurements of Mn2+-induced quenching of the intracellular fura-2 signal showed that BrcGMPdid not affect divalent cation entry in K+-stimulated preparations, whereas verapamil concentration dependently inhibited Mn2+ entry stimulated by K+-depolarization.6. The present results indicate that BrcGMP did not affect voltage-dependent Ca2+ channel gating in the rat aorta. For a given fura-2 Ca2+ signal, the contraction was lower in preparations exposed toBrcGMP than in the untreated ones, suggesting that the activation of cyclic GMP-dependent kinases reduced the contractile efficacy of calcium. Furthermore, the reduction of depolarization-dependent 45Ca2+ uptake reported with sodium nitroprusside, a NO donor, was not observed with biologically active concentrations of BrcGMP, suggesting that this drug could have additional mechanisms of action,unrelated to activation of protein G-kinase.

Animals↗
PubMed1995

Blood pressure-independent inhibition by lacidipine of endothelin-1-related cardiac hypertrophy in salt-loaded, stroke-prone spontaneously hypertensive rats.

We investigated the influence of salt loading on the renal and cardiac production of endothelin-1 (ET-1) in stroke-prone, spontaneously hypertensive rats (SHR-SP). The results show that the dietary salt intake did not change systolic blood pressure or the renal expression of the prepro-ET-1 mRNA but increased cardiac expression of the ET-1 gene transcript with concomitant ventricular hypertrophy. These changes were prevented by oral treatment with lacidipine, a long-lasting calcium antagonist, at a dose that did not reduce systolic blood pressure. This indicates that the cardioprotective properties of lacidipine may be dissociated from its blood pressure-lowering effect and could be related to inhibition of endothelin gene expression.

Animals↗
PubMed1993

Activity of dihydrothienopyridine S312 enantiomers on L-type Ca2+ channels in isolated rat aorta and cerebral microvessels.

The activity of the two enantiomers of the dihydrothienopyridine S312 was characterized in isolated rat aorta and cerebral microvessels. The interaction of S312 with 1,4-dihydropyridine and phenylalkylamine binding sites was also investigated in depolarized rat cerebral microvessels and in membranes from rat ileum. Both S-(+)-S312 and R-(-)-S312 dose dependently inhibited KCl-evoked contraction of the rat aorta, with IC50 values of 0.14 (0.13-0.16) and 2.98 (2.67-3.33) nM, respectively. When the aorta was preincubated with S-(+)-S312 in a depolarizing medium, the inhibitory effect was significantly increased, but this increased inhibition was not reversed by incubation in physiological medium. The effect of R-(-)-S312 was not affected by preincubation in a depolarizing medium. In rat cerebral microvessels, S-(+)-S312 inhibited the KCl-induced contraction and KCl-stimulated Ca2+ influx with similar potency. [3H](+)-PN 200-110 specific binding was competitively displaced by the two enantiomers in depolarized cerebral microvessels. The calculated Ki values were 0.12 nM for S-(+)-S312 and 2.4 nM for R-(-)-S312. Only 20% of [3H]D888 specific binding in rat ileum membranes was displaced by S-(+)-S312. The dissociation rate of [3H]D888 was markedly decreased by S-(+)-S312, and this allosteric interaction was significantly more marked than with nitrendipine. It is concluded that the dihydrothienopyridine S312 could interact with Ca2+ channels in a manner different to that of genuine dihydropyridines.

Animals↗
PubMed1993

Radioligand and functional estimates of the interaction of the 1,4-dihydropyridines, isradipine and lacidipine, with calcium channels in smooth muscle.

1. The present experiments were undertaken in order to characterize further the apparently irreversible inhibition of the contraction of depolarized rat aorta caused by lacidipine, a 1,4-dihydropyridine calcium antagonist. 2. We studied the effect of lacidipine on contraction evoked by 100 mM KCl solution in rat aorta, treated by N omega-nitro-L-arginine (0.1 mM), an inhibitor of nitric oxide (NO) synthesis. We compared the effect of prolonged depolarization on lacidipine and (+)-isradipine inhibition and the reversal of this inhibition after washout in the absence of dihydropyridines. Assuming that the onset of lacidipine-evoked inhibition was a pseudo-first order association kinetics, we estimated the dissociation rate constant (k-1 = 0.031 min-1), the association rate constant (k1 = 2.70 x 10(8) M-1 min-1) and the dissociation constant (KD = k-1/k1 = 115 pM) which was close to the IC50 value in steady-state conditions (160 pM). 3. The inhibitory effects of lacidipine and (+)-isradipine on rat aorta contraction were reversibly enhanced after preincubation with the drug in a 40 mM KCl-solution. Washout with drug-free 40 mM K(+)-depolarizing solution reversed inhibition in the (+)-isradipine-treated preparations, but not in the lacidipine-treated ones. 4. Radioligand binding studies were performed with [3H]-lacidipine and [3H]-isradipine in microsomes from rat aorta and rat ileum. Both ligands bound to a homogeneous population of binding sites (for[3H]-lacidipine: KD = 23 +/- 2.6 pM, Bmax = 380 +/- 21 fmol mg-1 protein in membranes from aorta; KD =23 +/- 3.1 pM, Bmax = 790 +/- 60 fmol mg-1 protein in membranes from ileum; for [3H]-isradipine:KD = 140 +/- 46 pM, Bmax = 350 +/- 64 fmol mg-1 protein in membrane from aorta; KD = 68 +/- 14 pM,Bmax = 760 +/- 75 fmol mg-1 protein in membranes from ileum). After isotopic dilution, [3H]-lacidipine and [3H]-isradipine dissociated according to a monoexponential kinetics. In membranes from ileum, the calculated dissociation rate constants (kappa_ 1) were 0.0257 min-1 and 0.0595 min-1, for [3H]-lacidipine and[3H]-isradipine, respectively.5. The non specific binding of [3H]-lacidipine and [3H]-isradipine, was measured in intact rat aorta preparations incubated under the conditions of the functional experiments, in the presence of nifedipine(1 microM). After incubation with [3H]-lacidipine 77.6 +/- 1.9 pM for 2 h the concentration of drug in the tissue was 15.15 +/- 1.18 fmol mg-1 w.wt. and still amounted to 7.24 +/- 0.61 fmol mg-1 w.wt. after 3.5 h washout in drug-free solution. After incubation with [3H]-isradipine 47.2 +/- 0.4 pM for 2 h it was 2.26 +/-0.07 fmol mg-1 w.wt. and was undetectable after 3.5 h washout in a drug-free solution.6. It is concluded that lacidipine interacts reversibly with dihydropyridine binding sites and that the apparent irreversible inhibition of contraction in depolarized preparations could be related to a nonspecific binding in a tissue compartment different from the plasma membrane.

Animals↗
PubMed1992

Selectivity scale of calcium antagonists in the human cardiovascular system based on in vitro studies.

The inhibitory effect of calcium antagonists has been studied on the calcium signal and on contractile activity in the human coronary and internal mammary arteries. We observed that rhythmic vasospasms, either spontaneous or evoked by serotonin and endothelin, were highly sensitive to calcium-channel inhibitors. Functional parameters describing the inhibition have been compared to binding parameters estimated in radioligand studies on membranes prepared from human coronary artery and from human heart. Taking the present studies and observations already published together, it was possible to build up a selectivity scale for diltiazem, verapamil, nifedipine, and nisoldipine. This showed that nisoldipine was more selective for coronary artery than the other calcium antagonists so far studied. Such a selectivity observed in functional studies on intact human preparations in vitro could be predicted considering the kinetic parameters of the interaction of nisoldipine with calcium channels.

Calcium↗
PubMed1992

A comparison of the potency of selective L-calcium channel blockers in human coronary and internal mammary arteries exposed to serotonin.

The actions of L-type calcium channel blockers on the contractile response to serotonin and to K(+)-depolarization have been studied in human coronary artery and in human internal mammary artery. The effect of ketanserin indicated that in both arteries serotonin action may be related not only to 5-serotonin2 but also to other serotonin receptors. In fura-2-loaded coronary and mammary arteries, exposed to serotonin (10 microM), nisoldipine (1 microM) and verapamil (10 microM) reversed completely the increase in [Ca++] cyt but not the contraction. The Ca++ antagonist-resistant contraction was equal to 26.2 +/- 2.1% of controls (n = 57) in coronary artery and to 51.7 +/- 4.2% (n = 19) in internal mammary artery. The concentration inhibiting by 50% the tonic contraction to serotonin sensitive to calcium channels blockade was 61-fold lower in human coronary artery than in human internal mammary artery with nisoldipine, but only 3.7-fold lower with nifedipine. There was no significant difference with diltiazem and verapamil. When human coronary artery and human internal mammary artery were exposed to a 100-mM KCl depolarizing solution, their sensitivity to nisoldipine was not significantly different. Preincubation with calcium antagonists in a 40-mM KCl solution reversibly increased the inhibitory effect of nisoldipine but not that of the other calcium antagonists. Comparison of radioligand and functional data shows that inhibition by calcium antagonists of the response to both serotonin and K(+)-depolarizing solution may be related to interaction with L-type calcium channels. The results indicate that the very high sensitivity to nisoldipine of the tonic response evoked by serotonin in human coronary artery might be related to the voltage-dependence of this dihydropyridine.

Adolescent↗
PubMed1991

Binding sites for 1,4-dihydropyridine Ca(2+)-channel modulators in rat intestinal smooth muscle.

The contractile response of intestinal smooth muscle to depolarization is characterized by a phasic and a tonic component which are differently sensitive to blockade by 1,4-dihydropyridines. As this difference in sensitivity could be related to different binding sites associated with distinct calcium channels, we analyzed the binding of the calciumantagonist 1,4-dihydropyridine (+)PN 200-110 [isopropyl-4-(2,1,3-benzodiazol-4-yl)-1,4-dihydro-2,6-dimethyl-5- methoxycarbonyl-pyridine-3-carboxylate] in longitudinal smooth muscle of the rat ileum. We carried out saturation binding experiments on intact tissue exposed to physiological and depolarizing (100 mmol l-1 K+) solution, and on different membrane fractions: the total microsomal fraction, the light microsomal fraction (enriched with plasma membranes) and the mitochondrial fraction. Binding of 3H(+)PN 200-110 to the intact longitudinal smooth muscle of rat ileum appeared to be voltage-dependent, KD decreased in depolarized tissue whereas Bmax was unchanged (change in membrane potential was assessed by measuring the distribution of 3H-tetraphenylphosphonium bromide). In membrane fractions two binding sites were detected, a high-affinity site associated with plasma membrane and a low-affinity site presumably associated with mitochondria (abundant in the fractions where the cytochrome c oxidase activity was high, and undetectable in the light microsomes poor in cytochrome c oxidase activity). The KD value of the high-affinity binding in isolated membrane fractions was similar to the KD value measured in intact depolarized tissue. The low affinity binding increased at high ionic strength and did not display any stereoselectivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Functional interaction of lacidipine with calcium channels in vascular smooth muscle.

We investigated the effect of lacidipine on 100-mM K(+)-evoked contractions and on 100-mM K(+)-evoked 45Ca2+ influx in rat aorta. Moreover, we compared the effect of prolonged depolarization on lacidipine inhibition and (+)isradipine inhibition of 100-mM K(+)-evoked contractions and the reversal of this inhibition by washing with a Ca(2+)-free physiological solution or with a Ca(2+)-free 40-mM K+ depolarizing solution. Lacidipine dose-dependently depressed the response to depolarization, and the pattern of inhibition was typical of voltage-dependent dihydropyridines. The concentration-inhibition curves on K(+)-evoked contraction and on K(+)-evoked 45Ca2+ influx were superimposed; the IC50 was 0.09 nM for the former and 0.11 nM for the latter. The inhibitory effect of lacidipine 60 pM or (+)isradipine 60 pM on rat aorta contraction was significantly enhanced when the preparations had been preincubated in the presence of the drugs in a K(+)-rich depolarizing solution. The inhibitory effect of lacidipine 60 pM or (+)isradipine 100 pM on rat aorta contraction was fully reversed after washing with a physiologic solution. When the washout was performed with a 40-mM K+ depolarizing solution, the inhibition was maintained in lacidipine-treated preparations, whereas it was reversed in the (+)isradipine treated ones. We conclude that lacidipine inhibits rat aorta contraction by interacting specifically with voltage-operated Ca2+ channels. Moreover, unlike with (+)isradipine, the complex formed with lacidipine and inactivated Ca2+ channels seems to not dissociate, because the inhibitory effect persisted in spite of removal of the drug from the depolarizing solution in which the arteries were immersed.

Animals↗
PubMed1989

Preliminary pharmacokinetic and clinical evaluation of ofloxacin in dental and oral cavity diseases.

In 14 healthy volunteers (8 M and 6 F), aged 19 to 33 years, serum and salivary concentrations of ofloxacin, administered in a single oral dose of 300 mg, were measured by high performance liquid chromatography (HPLC) and the microbiological agar diffusion method. The serum peak was observed at hour 1 (2.61 +/- 0.17 micrograms/ml), with a T1/2 of 4.14 h, a Kel of 0.167 h-1 and AUC of 15.07 micrograms/ml.h. The peak salivary concentration, obtained at hour 2, was 1.96 micrograms/ml, with a T1/2 of 4.40 h. Twenty dental patients (12 M and 8 F), aged 18 to 37 years, with various diseases, were treated orally with ofloxacin 600 mg/day for a period of four to six days. The clinical response proved excellent in one case, good in 16, fair in two and poor in one, with 85% efficacy rating. In five of these patients, ofloxacin concentrations in gingival tissue and alveolar bone were found to be 1.90 +/- 0.09 micrograms/g and 1.58 +/- 0.06 micrograms/g, respectively, while serum and salivary assays by HPLC confirmed the previous results. No changes of importance in haematochemical parameters were found in any of the patients. One patient only presented with diarrhoea and a skin rash which promptly cleared on discontinuing the therapy. Ofloxacin for its spectrum of action and good diffusion in the salivary and parodontal tissue compartment can be considered an useful tool in oral chemo-antibiotic therapy.

Adolescent↗