Archives internationales de pharmacodynamie et de therapie最新文献

The effects of Gly-His-Lys-Cu and of three synthetic analogues (I, II and III) on wound healing of the guinea-pig dorsal skin, as well as on cultured fibroblasts, were examined. Gly-His-Lys-Cu and peptide I-Cu were tested in vivo. Hydroxyproline, proteins, DNA and semicarbazide-sensitive amine oxidase, with a high affinity for benzylamine, were measured, and the histology of the wounds was observed after staining with hematoxylin/eosin. Another set of wounds was treated in parallel with equivalent amounts of copper acetate. Gly-His-Lys-Cu and the analogues caused a decrease of the activity of semicarbazide-sensitive amine oxidase, with a high affinity for benzylamine, 4-8 days after surgery, followed by an increase on day 11 that was higher than in the control group. No significant difference was found between the two peptides. A slower reorganization of the skin and a delayed activation of fibroblasts are the main effects observed with these peptides-Cu complexes. Preliminary studies on cultured fibroblasts were monitored to see whether these peptides had a direct effect on fibroblasts. The products studied at a concentration of 10(-7) M, decreased cell reproduction and increased collagen expression.

A calcium entry blocker, nifedipine, or an intracellular calcium release inhibitor TMB-8, was infused into the renal artery before and during intravenous infusion of angiotensin II in anesthetized dogs. In the control period, nifedipine (0.1 microgram/kg/min) or TMB-8 (75 micrograms/kg/min) increased urine flow rate, urinary sodium excretion and fractional sodium excretion, with little change in renal blood flow or glomerular filtration rate. Angiotensin II (10 ng/kg/min) elevated blood pressure and reduced urine flow rate, urinary sodium excretion and fractional sodium excretion. In the angiotensin II infusion period, nifedipine increased urine flow rate, urinary sodium excretion and fractional sodium excretion to levels higher than those observed in the control period. TMB-8 also caused augmented urinary responses. The results suggest that the angiotensin II-induced antinatriuresis depends both on the calcium influx through dihydropyridine-sensitive calcium channels, and on the calcium release from TMB-8-sensitive calcium stores at the renal tubular sites.

We studied the effect of dilazep on the binding of [3H]- batrachotoxinin A 20 alpha-benzoate ([3H]BTXB), which binds to and stabilizes the activated state of the Na+ channel, and compared it with that of lidocaine in canine cardiac sarcolemmal vesicles. Dilazep inhibited the specific [3H]BTXB binding in a dose-dependent manner with an IC50 value of 0.37 microM, while lidocaine inhibited it with an IC50 value of 92 microM. Scatchard analysis of [3H]BTXB binding demonstrated that both dilazep and lidocaine reduced the amax without a marked effect on the K(D). The inhibition of [3H]BTXB induced by dilazep was reversible. Both dilazep (4 microM) and lidocaine (100 microM) increased the dissociation rate constant of [3H]BTXB only in concentrations which are about a 10-fold greater than their IC50, indicating the low affinity of both drugs for the [3H]BTXB-bound Na+ channel. However, dilazep (0.5 microM) and lidocaine (100 microM) decreased significantly the association rate constant of the [3H]BTXB binding at concentrations near their IC50, indicating that the affinity of both drugs for the [3H]BTXB-unbound Na+ channel is relatively high. These results suggest that, in canine cardiac membrane vesicles, the effect of dilazep in inhibiting the binding of [3H]BTXB and stabilizing the Na+ channel is similar to that of lidocaine, but the potency of dilazep is greater than that of lidocaine.

The effects of age on alpha1-adrenoceptor and Ca2+ channel-mediated contractile mechanisms in the thoracic aorta, isolated from rats of 3, 6, 10, 18 and 40 weeks old, were studied. The potency (pD(2) value) of norepinephrine increased with age from 3 to 10 weeks, but decreased thereafter from 10 to 40 weeks. The change in pD(2) value of norepinephrine was proportional to the logarithm of the maximum number of binding sites (B(max)), obtained in the [(3)H]prazosin binding study. The inhibitory effect of a potent Ca(2)+ channel blocker, israpidine, on the norepinephrine-induced contraction decreased with age from 3 to 10 weeks, but increased in rats aged 10 to 40 weeks. An inverse relationship between the change in isradipine inhibition, the maximum reduction of isradipine on norepinephrine-induced contraction and the logarithm of B(max) was found. The inhibitory effect of a nonselective Ca2+ channel blocker, SKF96365, on the norepinephrine-induced contraction did not change with age. The amplitude of the Ca2+-induced sustained contraction, after pretreatment with isradipine (10(-7) M) in the presence of norepinephrine (10(-6) M), increased with age from 3 to 10 weeks, but decreased thereafter in rats aged 10 to 40 weeks. There was no significant difference in the slope of the regression lines between the cytosolic Ca(2)+ level ([Ca2+]i) and the tension in the presence of norepinephrine at different ages. These results suggest that the changes in alpha(1)-adrenoceptor mechanisms and the reduction by isradipine with age are due to changes in the alpha1-adrenoceptor density and the population of Ca2+ channels, but not to changes in the affinity of drugs to the alpha1-adrenoceptor or Ca2+ sensitivity of contractile elements of aortic smooth muscles.

The electrophysiological effects of MPC-1304, a novel calcium antagonist, were examined using the conventional microelectrode and whole-cell patch-clamp techniques in guinea-pig hearts. MPC-1304, at 100 nM or higher concentrations, produced a dose-dependent reduction in the action potential duration of guinea-pig papillary muscles, without changes in resting membrane potentials and maximum rate of rise of action potentials. In guinea-pig ventricular myocytes, MPC-1304 (1-100 nM) dose-dependently depressed the initial inward currents induced by depolarizing pulses from a holding potential of -30 mV in the external Tyrode solution, as did nifedipine, whereas the late outward current was not changed by MPC-1304. In the presence of 100 nM of MPC-1304 or 100 nM of nifedipine, the first depolarizing pulse from a holding potential of -80 mV caused a depression of the isolated L-type Ca2+ current (I(Ca)) by 29.5 % and 29.4 % of the control, respectively (tonic block), and successive pulses further suppressed I(Ca) in a use-dependent manner (use-dependent block). The degree of steady state use-dependent block of I(Ca) by 100 nM of MPC-1304 was 25.5 % at the stimulus frequency of 1 Hz and further increased to 34.0 % at 2 Hz (frequency-dependent block), which were significantly larger than those by 100 nM of nifedipine at both frequencies. The onset rate of use-dependent block by 100 nM MPC-1304 was significantly smaller than that by 100 nM nifedipine. MPC-1304 (100 nM) and nifedipine (100 nM) shifted the steady state inactivation curve of I(Ca) toward the negative potential by 3.3 mV and 9.1 mV in the mid-potential of the curve, respectively. The estimated dissociation constants of MPC-1304 were 137.7 and 49.9 nM for the resting and inactivated states of the L-type Ca2+ channel, respectively, and those of nifedipine were 113.9 and 18.1 nM, respectively. We conclude that MPC-1304 suppress the L-type Ca2+ channel with slow kinetics in a voltage- and frequency-dependent manner, which might be caused by its high affinity to the activated as well as to the inactivated state of the channel.

The effects of the L-type calcium channel blockers, nicardipine, nimodipine, nilvadipine and amlodipine, on brain dysfunction were examined in senescence-accelerated-prone mice. A disturbed brain function in passive avoidance response, forced swimming, rota-rod and traction tests was observed in senescence-accelerated-prone mice compared to senescence-accelerated-resistant mice. A single oral administration of the four calcium channel blockers tested had little effect on the brain dysfunction in senescence-accelerated-prone mice. In contrast, the daily oral administration of nicardipine (1 and 3 mg/kg), nimodipine (3 mg/kg) and nilvadipine (3 mg/kg), once a day for three weeks, prolonged the shortened latency of step-through in the passive avoidance response and falling time in rota-rod tests. Brain dysfunction in forced swimming and traction tests was not influenced by repeated administration of these blockers. Repeated administration of amlodipine for three weeks in senescence-accelerated-prone mice showed little pharmacological actions in all four tests. Thus, we found that repeated administration of nicardipine, nimodipine and nilvadipine ameliorated the brain dysfunction in these mice. Furthermore, the present study suggests that senescence-accelerated-prone mice can be used as an appropriate model for evaluating the pharmacological effects of calcium channel blockers on brain dysfunction.

Incubation of endothelium-denuded rings of rat aorta at 37 degrees C for 18 hours in Krebs solution led to a profound depression of the contractile actions of phenylephrine (1 nM-10 mu M). A major component of this depression of vasoconstriction was due to the relaxant actions of nitric oxide since it was reversed following inhibition of the synthesis of nitric oxide with N(G)-nitro-L-arginine methyl ester or its actions with haemoglobin (30 microM) or methylene blue (10 mu M). The depression was also reversed upon treatment with LY83583 (0.1-1 microM which generates superoxide anions, intracellularly and extracellularly, but was unaffected by hypoxanthine (100 microM)/ xanthine oxidase (16 mu/ml) which generates superoxide anion only extracellularly. The ability of polymixin B (30 microM) to inhibit the development of the depression of vasoconstriction suggests that it results from the expression of an inducible form of nitric oxide synthase, stimulated by bacterial lipopolysaccharide, contaminating the Krebs solution. In contrast to aortic rings, we found that lipopolysaccharide (10-10,000 ng/ml) alone from S. typhosa was unable to stimulate the expression of the inducible form of nitric oxide synthase in rat aortic smooth muscle cells grown in culture from explant, as assessed either by measuring the accumulation of nitrite into the culture medium during a 24 hour incubation period or by measuring the smooth muscle cyclic GMP content. Interferon-gamma (1-100 IU/ml) and interleukin-1 alpha (1-10 IU/ml) alone were, however, able to stimulate the accumulation of nitrite in a concentration-dependent manner. These inductions of nitrite accumulation were abolished following treatment with N(G)-nitro-(L)-arginine methyl ester (1 mM) and dexamethasone (1 microM). Further investigations are required to determine whether the ability of bacterial lipopolysaccharide to induce the inducible form of nitric oxide synthase in rat aortic rings, but not in rat aortic smooth muscle cells in culture, results from the presence of an endotoxin-sensitive, cytokine-secreting cell type in the vessel wall which is absent in culture, or from differences in smooth muscle phenotype in situ and in culture.

In the present study, we explored whether or not a neutral endopeptidase inhibitor provokes cough in awake guinea-pigs. Inhalation of phosphoramidon at a concentration of 10(-6) M did not cause cough, but increasing the concentration to 10(-5) M caused cough with a latency of about 10 to 12 min. Inhalation of enalapril, an angiotensin-converting enzyme inhibitor, did not cause cough, even at high concentrations of 10(-5) M and 10(-4) M. Pretreatment with phosphoramidon (10(-5) M) significantly increased the number of coughs caused by substance P and capsaicin. Capsaicin-induced coughs were more easily produced in bronchitic guinea-pigs than in normal guinea-pigs. However, there was no significant difference in the number of phosphoramidon-induced coughs between normal and bronchitic guinea-pigs. Phosphoramidon-induced coughs were significantly depressed by codeine (20 mg/kg, p.o.) and CP96345 (2 mg/kg, i.v.). The present results provide new evidence for the proposed idea that neutral endopeptidase may regulate the occurrence of cough.

Species differences in the 5-hydroxytryptamine (5-HT)3 receptor among anesthetized rats, mice, rabbits, ferrets, dogs and guinea-pigs were examined in the transient bradycardia induced by i.v. injection of 5-HT (the von Bezold-Jarisch reflex). We also investigated the mechanism of the 5-HT-induced bradycardia in these species. 5-Hydroxytryptamine and the selective 5-HT3 receptor agonists, 2-methyl-5-HT and m-chlorophenylbiguanide, dosedependently decreased heart rate in all species. In anesthetized rats, mice, ferrets and guinea-pigs, 2-methyl-5-HT and m-chlorophenylbiguanide behaved as full agonists against the 5-HT3 receptor, whereas their agonistic action in rabbits was partial. On the basis of ED50 values, there was no marked species difference in the potency of 5-HT3 receptor agonists. In contrast, the blocking activities of the 5-HT3 receptor antagonists, YM060, YM114 (KAE-393), granisetron and ondansetron, were markedly weaker in anesthetized guinea-pigs than in the other species. With regard to the mechanism of the 5-HT-induced bradycardia, YM060, atropine or vagotomy completely inhibited the 5-HT-induced bradycardia in anesthetized rats and mice. In guinea-pigs, in contrast, higher doses of YM060 and atropine or vagotomy inhibited this reflex by approximately 80%. Although the YM060-resistant part of the 5-HT-induced bradycardia in guinea-pigs was affected by neither 5-HT2 receptor antagonists nor 5-HT4 receptor antagonists, it was completely abolished by methysergide, a 5-HT1-like and 5-HT2 receptor antagonist. These results suggest that there is a species difference in the 5-HT3 receptor between guinea-pigs and other species in the von Bezold-Jarisch reflex system. They also suggest that the 5-HT-induced bradycardia in anesthetized rats and mice is evoked by acetylcholine released through activation of 5-HT3 receptors on the vagus nerve, while that in guinea-pigs is, at least in part, mediated through 5-HT1-like receptors in addition to 5-HT3 receptors.

The recently synthesized benzofuranylethanolamines GE 68, GE 70, GE 76, RG 16 and RG 25, were studied in guinea-pig isolated papillary muscles and right atria. With regard to their inotropic, chronotropic and beta-adrenoceptor-blocking activity, these compounds were compared with the reference drug propafenone. GE 68, GE 70 and GE 76 were almost equally potent as propafenone in reducing the isometric force of contraction of papillary muscles, while RG 16 and RG 25 were less effective than the parent drug. GE 70 decreased the spontaneous rate of activity of right atria in a similar concentration range as propafenone, whereas GE 68 showed a more, and GE 76, RG 16 and RG 25 a less pronounced negative chronotropy. In contrast to the reference compound propafenone, the derivatives GE 70, GE 76 and RG 16 lacked any beta-adrenoceptor-blocking activity, while GE 68 and RG 25 exerted only a weak and nonsignificant effect. It is concluded that the formation of a benzofurane ring in the propafenone molecule did not cause a prominent change in negative inotropic and negative chronotropic effects, but resulted in a decrease or loss of beta-adrenoceptor-blocking activity. Additionally, an exchange of the phenylethyl group (GE 68, GE 70, GE 76) on the benzofurane ring by a methyl (RG 25) or ethyl group (RG 16), attenuated the negative inotropic and chronotropic potency.