General Pharmacology-the Vascular System最新文献

Mistletoe lectins are of high biological activity and exert cytotoxic effects. We have previously shown that Korean mistletoe, Viscum album var. coloratum, lectin-II specifically induces apoptotic cell death in cancer cells, not normal lymphocytes. The destructive mechanism by mistletoe lectins on tumor cells was mediated by activation of c-JUN N-terminal kinase (JNK)/stress-activated protein kinase. Herein, we investigated the involvement of caspase cascade and its proteolytic cleavage effects on biosubstrates of human myeloleukemic U937 cells by d-galactoside and N-acetyl-galactosamine-specific Korean mistletoe lectin-II. Mistletoe lectin-II induced ladder pattern DNA fragmentation and activation of caspase-3, -8, and -9 of U937 cells, but not caspase-1 protease, in a time- and dose-dependent manner. Consistent with catalytic activation of protease, both poly(ADP-ribose) polymerase (PARP) and protein kinase C-δ (PKC-δ) are also cleaved in mistletoe lectin-II-treated U937 cells. An inhibitor of caspase-3-like protease, DEVD-CHO peptide, significantly inhibited mistletoe lectin-II-induced apoptosis, PARP cleavage, and fragmentation of DNA. These results provide the evidence that Korean mistletoe lectin-II induces apoptotic death of U937 cells via activation of caspase cascades.

The present study was undertaken to determine the therapeutic effect of the culture filtrate of Cryptococcus neoformans var. gattii (CneF) in experimental immune complex glomerulonephritis. Bovine serum albumin (BSA) nephritis was induced in rats by a subcutaneous immunization and daily intravenous administration of BSA. CneF solution at three different doses (36, 54, and 90 mg/kg based on carbohydrate concentration) was administered intraperitoneally at regular 72-h intervals for 4 weeks. Onset of treatment was day 65, and urinary protein was measured at different intervals. Animals were euthanized on day 107. Serum and urine determinants were measured at the time of sacrifice and kidney specimens were examined. Results of this experiment showed that CneF therapy could significantly reduce the urinary protein excretion, blood urea nitrogen (BUN), plasma concentration of triglyceride, and increase the serum HDL cholesterol in treated rats vs. nontreated controls. Moreover, there was significant difference in glomerular changes between treated and nontreated groups. These observations show that the beneficial effect of CneF may be related to decreased number of glomerular leukocytes. Our findings suggest that treatment with CneF as a new antiinflammatory compound can reduce proteinuria, suppress the development of glomerular lesions, and exert lipid-lowering property in a rat model of immune complex glomerulonephritis.

In the perfused rat uterine vascular bed, 5-hydroxytryptamine (5-HT) produced dose-dependent vasoconstrictor responses. Buspirone, a selective 5-HT_1A receptor agonist, was not effective at low doses but produced a response at high doses. When perfusion pressure was raised with phenylephrine, responses to 5-HT were enhanced while buspirone produced dose-dependent vasodilator responses. Buspirone did not produce vasodilation when perfusion pressure was raised with vasopressin or U46619. Buspirone-induced vasodilator responses were not affected by selective 5-HT_1A receptor antagonists, 8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4,5]-decane-7,9-dione (BMY 7378) and N-tert-butyl-3-(4-[2-methoxyphenyl]piperazin-1-yl)-2-phenylpropanamide (WAY 100478), indicating that specific 5-HT_1A receptors might not be involved in buspirone-induced vasodilation. Buspirone (3×10⁻⁵ M) and prazosin (3×10⁻⁹ M) antagonized noradrenaline-induced constriction with dose ratios of 19.1±2.9 and 11.7±2.1, respectively. The dose ratio of these antagonists in combination was 46.6±8.1. Since the combination ratio is closer to the sum of their individual dose ratios less 2 (i.e. DR_p+DR_b−2) than it is to the product of their individual dose ratios, our data suggest an interaction of buspirone with α₁-adrenoceptors. Buspirone also protected adrenoceptors against inactivation by phenoxybenzamine confirming that buspirone interacted with α₁-adrenoceptors. We concluded that buspirone-induced vasodilation of the perfused rat uterine vascular bed is mediated through blockade of α₁-adrenoceptors rather than through 5-HT_1A receptors.

This study characterizes the reactivity of human chorionic plate vein in full-term (39.4±0.3 weeks of gestation) and preterm (34.4±0.6 weeks of gestation) pregnancy to endothelin-1 (ET-1) and attempts to characterize ET-1 receptor subtype, and the contribution of nitric oxide and cyclooxygenase products in these responses. In placental veins from full-term and preterm pregnant women, cumulative addition of ET-1 (10⁻¹⁰–10⁻⁶ M) caused marked and long-lasting concentration-dependent contractile responses. The mean EC₅₀ and E_max values for ET-1-induced venoconstriction did not differ between the full-term and preterm pregnancy groups. In the veins from preterm placental preparations, the ET_A receptor-selective antagonist cyclo(d-α-aspartyl-l-propyl-d-valyl-l-leucyl-d-tryptophyl (BQ123) reduced the ET-1-induced contraction by 28.6±2.4%, compared to a decline in tension of 51.2±4.2% in the full-term placental vessels. The ET_B receptor-selective antagonist, N-[N-[N-[2,6-dimethyl-1piperidinyl)carbonyl]-4-methyl-l-leucyl]-1-(methoxycarbonyl)-d-tryptophyl]-d-norleucinemonosodium (BQ788), did not influence ET-1-induced contraction in placental vein from both pregnancy groups in terms of maximal contraction and sensitivity. Pretreatment with the cyclooxygenase inhibitor, indomethacin (1 μM) and the nitric oxide synthase inhibitor N^w-nitro-l-arginine (NOLA, 100 μM) did not significantly affect either the EC₅₀ or the maximum contraction to ET-1 in veins from normal full-term and preterm preparations. The results of this study suggest that there is no correlation between ET-1-induced vasoconstriction and gestational age and that this vasoconstriction is mediated predominantly via ET_A receptor subtype in both groups of pregnant women, independent of NO and eicosanoids.

(1) The vasorelaxation produced by the phosphodiesterase 3 (PDE3) inhibitor, amrinone was investigated in isolated rat aorta denuded of endothelium. In the presence of extracellular Ca²⁺, amrinone, milrinone and 3-isobutyl-1-methylxanthine (IBMX), relaxed endothelium-denuded rat aortic rings constricted with phenylephrine. While the actions of milrinone and IBMX were inhibited by the protein kinase G (PKG) inhibitor, Rp-8-Bromo guanosine-3′,5′ monophosphothioate (Rp-8-Br-cGMPS; 0.5 mM), that of amrinone was only slightly affected; whereas the protein kinase A (PKA) inhibitor, Rp-adenosine-3′,5′ cyclic monophosphothioate (Rp-cAMPS; 0.5 mM) had no effect on any agent. (2) Amrinone (100 μM) inhibited ⁴⁵Ca²⁺ influx through receptor- or store-operated Ca²⁺ channels following stimulation with phenylephrine (1 μM) or thapsigargin (1 μM). In contrast, amrinone had no effect on KCl (120 mM)-stimulated Ca²⁺ influx. (3) In the absence of extracellular Ca²⁺, amrinone (30 μM) inhibited the constriction produced by phenylephrine, 5-hydroxytryptamine (5HT) and U46619, and this effect was not affected by Rp-cAMPS or Rp-8-Br-cGMPS. (4) The intracellular mechanism of action of amrinone may involve the phospholipase C (PLC)-inositol 1,4,5 trisphosphate (IP₃)-intracellular Ca²⁺ signal transduction pathway. However, amrinone (100 μM) had no effect on either basal- or noradrenaline (100 μM)-stimulated PLC activity. Similarly, IP₃ stimulated a concentration-dependent release of Ca²⁺ from rat brain microsomes that was not affected by amrinone (30 and 100 μM). (5) In conclusion, the vasorelaxant action of amrinone does not involve adenosine 3′,5′ cyclic monophosphate (cAMP) or involve guanosine 3′,5′ cyclic monophosphate (cGMP) but may include an inhibition of Ca²⁺ influx through receptor- or store-operated Ca²⁺ channels, although it does not directly affect intracellular Ca²⁺ release.

Electrical field stimulation (4 Hz, 0.2 ms, 70 V supramaximal voltage, 10 s duration) produced contraction of perfused rabbit central ear arteries, and this contraction was reduced by incubation with insulin (0.6–200 mU/ml). This inhibitory effect of insulin was not significantly modified by removing the endothelium, or by treatment with N^W-nitro-l-arginine (l-NA, 10⁻⁴ M), meclofenamate (10⁻⁵ M), ouabain (10⁻⁶ M), or cocaine (10⁻⁵ M). Insulin (200 mU/ml) did not modify the vascular contraction due to exogenous norepinephrine (10⁻⁸–10⁻⁴ M) nor the relaxation due to acetylcholine (10⁻⁸–10⁻⁴ M). This suggests that insulin may reduce vascular contraction by sympathetic stimulation, and this effect is not dependent on endothelial nitric oxide, prostanoids, or Na⁺–K⁺ pump activation.

Agmatine, a product of arginine metabolism in vascular endothelial cells, is structurally similar to the natural polyamines, putrescine, spermidine and spermine. To test the hypothesis that agmatine and polyamines interacted at the level of the polyamine transporter, we determined if polyamines competed with agmatine for import and whether interventions modulating polyamine import exerted coordinate effects on agmatine uptake. Multiple lines of evidence were obtained to suggest that agmatine enters pulmonary artery endothelial cells (PAECs) via the polyamine transporter, though its intracellular disposition after uptake appears different from the natural polyamines.

In this work, we have studied the pharmacokinetics and milk penetration of verapamil following intravenous administration in lactating rabbits. Milk-to-serum drug concentration ratios (M/B_obs) have been determined using area under the milk and serum concentration–time profiles, and the resulting values have then been compared with those obtained by theoretical classical diffusion milk transfer models that were described by Fleishaker et al. [J. Pharm. Sci. 76 (1987) 189.], Atkinson and Begg [Br. J. Clin. Pharmacol. 25 (1990) 495.], and Stebler and Guentert [Pharm. Res. 9 (1992) 1299.]. The pharmacokinetic profile of verapamil in lactating rabbits following endovenous administration is described in the form of a two-compartment model. Moreover, we detected an important milk transfer after endovenous administration of verapamil in lactating rabbits. M/B_obs was near 15. The classical diffusional models mentioned were not able to predict this extensive transfer of verapamil into rabbit milk. However, when the classical Fleishaker equation was modified and a stepwise regression was carried out, we found that the M/B_obs value could be predicted using the plasma and milk protein binding.

Relaxations to acetylcholine and contractions to acetylcholine in the presence of the nitric oxide (NO) synthesis inhibitor (l-N^G-nitroarginine methyl ester, l-NAME) were studied in aortic rings from rabbits fed either a control or a diet containing 0.5% cholesterol+14% coconut oil for 14 weeks and treated or not with atorvastatin (2.5 mg kg⁻¹ day⁻¹). Rings were incubated with the endothelin (ET_A) receptor antagonist BQ123, and/or the thromboxane A₂ (TXA₂)/prostaglandin H₂ (PGH₂) receptor antagonist ifetroban. In rabbits, high cholesterol and triglyceride plasma levels were associated with intimal thickening and blunted acetylcholine-relaxation as compared with controls. By contrast, acetylcholine+l-NAME response was higher. Incubation with either ifetroban or BQ123 increased acetylcholine-relaxation in both diet groups and it reduced the constrictor response only in dyslipidemic rabbits. Removal of endothelium reduced acetylcholine+l-NAME contraction in dyslipidemic rabbits, although increased it in control animals. Atorvastatin treatment reduced plasma lipid levels and lesion size in dyslipidemic animals. Likewise, it prevented acetylcholine-relaxation reduction. In addition, atorvastatin reduced constrictor response in dyslipidemic rabbits but only in rings with endothelium. Incubation with either ifetroban or BQ123 did not further modify these responses in atorvastatin-treated animals in any group. These data suggest that ET and TXA₂ availabilities seem to participate in the endothelial dysfunction associated with dyslipidemia. Atorvastatin treatment reduces intimal thickening and improves endothelial dysfunction in rabbits. This effect seems to be a consequence of its ability to act on ET and TXA₂ systems.