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Electrocardiographic QTc intervals were measured in twenty-one hypercholesterolemic patients before and after long-term probucol (500-1,000 mg/day for 30 months) treatment. Probucol reduced serum total cholesterol (TC), triglyceride (TG), and high density lipoprotein-cholesterol (HDL-C). Mean QTc interval prolongation after probucol was 17 msec. A positive correlation was found between the change in QTc interval after probucol (delta QTc) and the total amount of probucol administered. delta QTc was negatively correlated to the pre-treatment QTc interval. No correlation was observed between serum probucol concentrations and delta QTc. Neither clinical evidence of cardiotoxicity nor critical arrhythmias were noted during the treatment period.

Human parathyroid hormone (hPTH (1-38)) induced concentration-dependent relaxations in prostaglandin F2 alpha-preconstricted pig coronary arteries in vitro. Removal of endothelial cells or pretreatment with nitro-L-arginine, a specific inhibitor of the endothelium-derived relaxing factor (EDRF) synthesis, impaired, although to a small extent, hPTH-induced relaxations. Human PTH-, but not bradykinin- or nitroglycerin-induced relaxations were potentiated in the presence of the cyclic AMP phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX). Human PTH also relaxed preconstricted human inferior epigastric arteries in vitro. In accordance to pig coronary arteries, this relaxation was potentiated in the presence of IBMX. However, the human internal thoracic (mammary) artery did not respond to hPTH (1-100 nM). Thus, acute vasodilatory effects of hPTH may not be present in all human arteries. The physiological significance of this phenomenon is not known. This relaxation, at least in pig arteries, is mediated to a small extent by the release of EDRF. In addition, this relaxation appears to be mainly mediated in both pig and human arteries by a smooth muscle cyclic AMP pathway.

Acetazolamide (AZ), the selective inhibitor of carbonic anhydrase, was proved by intravenous Xenon 133 technique to increase cerebral blood flow (CBF). In this study cerebrovascular reactivity to AZ was evaluated in 10 normal subjects by transcranial Doppler (TCD) within the middle cerebral artery (MCA), since several reports have demonstrated that velocity of cerebral blood flow is well correlated to CBF. After 1 gr AZ injection blood flow velocity markedly increased in all subjects, with a peak in both systolic and diastolic velocity 20 min after drug administration. At that time systolic velocity increased by 35% and diastolic velocity by 50% in comparison to basal values. In contrast with Xenon 133 technique which gives one measurement only for each investigation, TCD allows a continuous monitoring of haemodynamic change following AZ infusion. MCA diastolic velocity at rest was inversely related to age (r = -.804, p < 0.01); baseline diastolic velocity was inversely related to the maximum percentage increment (r = -.745 p < .05). No change in blood pressure and heart rate was observed under experimental conditions. These results, confirm the usefulness of the AZ test in the evaluation of cerebrovascular reactivity and strongly support the use of TCD technique applied to AZ in order to investigate cerebrovascular haemodynamics in normal healthy subjects and in patients at risk of cerebrovascular insufficiency.

Athymic nude mice are characterized by deficient cellular immunity due to almost complete absence of functional mature T-lymphocytes. Plasma HDL (the major cholesterol carrier in mice) cholesterol levels in nude mice were found to be reduced by 1.7 fold in comparison to control Balb/c mice. Cellular degradation of HDL by peritoneal macrophages (MPM) that were obtained from nude mice, was 2.5 fold greater in comparison to MPM obtained from Balb/c mice. Since nude mice lack cytokines that can affect lipid metabolism, intravenous administration of 10 micrograms/100g body weight of interleukin-1 (IL-1), tumor necrosis factor (TNF), or transforming growth factor (TGF) on HDL degradation by their PM, were investigated. IL-1 (but not TNF) reduced HDL (50 micrograms of protein/ml) cellular degradation from 810 +/- 34 to 350 +/- 12 ng/mg cell protein (p < 0.01) in nude mice. In control Balb/c mice, however, IL-1 as well as TNF enhanced macrophage degradation of HDL by 56% and 280%, respectively. TGF injection into nude mice (but not control mice) decreased HDL degradation by their MPM by 50%. We, thus, suggest that in nude mice the reduced plasma and HDL cholesterol levels are probably due to increased HDL degradation, which may be secondary to IL-1 and TGF deficiency.

This study examined the reversibility of chronic ethanol induced increase in systolic blood pressure, elevated platelet cytosolic free calcium and aortic calcium uptake in rats and the effect of a calcium channel blocker on these changes. Twenty-four male Wistar-Kyoto rats, age 7 weeks, were divided into 4 groups of 6 animals each. Animals in group I were given water and group II, III and IV, 5% ethanol in drinking water for the next 7 weeks. Systolic blood pressure in the ethanol treated rats was significantly higher (p < 0.01) than in controls after 1 week and remained higher. After 7 weeks, group I was continued on water, group II on ethanol, group III was continued on ethanol but with the addition of verapamil 5 mg/100 ml in their drinking water and group IV was returned to normal drinking water for the next 7 weeks. After 14 weeks, systolic blood pressure, platelet cytosolic free calcium and aortic calcium uptake was significantly higher (p < 0.01) in rats given ethanol for 14 weeks and also in rats given ethanol for 7 weeks followed by water for 7 weeks as compared to controls. These two groups also showed smooth muscle cell hyperplasia with some thickening of the wall and narrowing of the lumen in small arteries and arterioles of kidney. Verapamil given to the ethanol treated rats normalized their blood pressure, platelet cytosolic free calcium, aortic calcium uptake and attenuated renal vascular changes. Discontinuation of ethanol treatment for 7 weeks did not reverse the hypertension or the adverse renal vascular changes in ethanol induced hypertensive rats.

The purpose of this study was to evaluate, under the most rigorous precautionary measures against in vitro oxidation, whether the baseline lipid peroxide levels in hypercholesterolemic subjects were higher than those in normolipidemic subjects. Two methods were employed: thiobarbituric acid (TBA), and hemoglobin-methylene blue (HbMB). Blood was collected into EDTA tube and centrifuged at 4 degrees C for 30 min to collect plasma, then protected from in vitro oxidation with preservatives and N2. Serum was from blood samples allowed to clot at 20 degrees C for 1 h, then protected from oxidation. Determination of lipid peroxide was carried out within 2 h of blood collection. Results from 35 hypercholesterolemic and 34 control subjects showed that lipid peroxide levels obtained from both methods were significantly higher in serum than in plasma for both groups, suggesting a greater rate of lipid peroxidation occurred in serum during clot formation. However, no significant difference in lipid peroxide levels was found between patients and controls in either serum or plasma by either assay method. No correlation existed between lipid peroxide values and plasma cholesterol or LDL-cholesterol levels. These results suggest that the mechanism for a higher tendency towards atherosclerosis in hypercholesterolemic subjects is not related to baseline levels of plasma lipid peroxide.

The metabolism of three low density lipoprotein (LDL) subfractions by human monocyte-derived macrophages (HMDM) through the LDL receptor pathway was studied. The three LDL subfractions, very light LDL1, light LDL2 and heavy LDL3, were isolated from serum pools of normolipidemic subjects by density gradient ultracentrifugation. The LDL subfractions were shown to differ in molecular size and chemical composition but not in electrophoretic mobility on agarose gel. Cell specific association, cell specific degradation and stimulation of cholesteryl esterification were determined in parallel after incubation of HMDM with increasing amounts of LDL-protein of the three LDL subfractions. The experiments were repeated four times with freshly prepared LDL subfractions. Both the cell specific association and degradation increased more with increasing LDL-protein concentration for LDL1 than for LDL3 (p < 0.001). The results for LDL2 were intermediate between those for LDL1 and LDL3 and differed significantly from both (p < 0.05). For the stimulation of cholesteryl ester formation, the curves for LDL1 and LDL2 increased more with increasing LDL-protein concentration than that for LDL3 (p < 0.001); the results for LDL1 and LDL2 did not differ significantly from each other. These differences between LDL subfractions in cholesteryl esterification were independent of the cholesterol content of the LDL subfractions. The results show that LDL subfractions have different rates of LDL receptor-mediated catabolism by HMDM. As HMDM play an important role in the formation of atherosclerotic plaques, the differences between the LDL subfractions in catabolism by HMDM, may result in differences in atherogenicity between LDL subfractions isolated from normolipidemic subjects.

The purpose of this study is to better understand how hyperlipidemia alters the modulating action of prostaglandin E1 (PGE1) on platelet function. Using our previously characterized rat model of atherogenesis, we demonstrate that the parenteral lipid emulsions, Lipofundin-S and Liposyn, significantly (p < or = 0.05) enhance baseline platelet aggregation. In addition, dose response curves show that in all animals, PGE1 substantially inhibits platelet aggregation at 10(-7) to 10(-6) M, while significantly stimulating platelet function at lower doses. However, at all PGE1 concentrations, aggregation values are higher in platelets from lipid-treated vs. control rats, showing that hyperlipidemia significantly reduces the ability of high concentrations of PGE1 to inhibit platelet activity, based on the absolute values of the controls. Also, dose response curves for PGE1 on platelet aggregation show a marked similarity in shape for control ratsvs. normal humans. Thus, this study demonstrates that hyperlipidemia significantly alters the platelet modulating action of prostaglandin E1, and it shows that PGE1 can either inhibit or stimulate platelet activity in both rat and human platelets.

The purpose of this study was to examine the effect of dietary cholesterol on the total blood cholesterol levels of nondiabetic and streptozotocin-diabetic rats. Thirty-six Sprague-Dawley rats were divided into four groups: nondiabetic/control diet (C), streptozotocin-diabetic/control diet (D), nondiabetic/control diet + 2% cholesterol (CH), and streptozotocin-diabetic/control diet + 2% cholesterol (DH). Plasma cholesterol levels were not significantly elevated in the D group (63.4 +/- 9.0 mg/dl) when compared with the C group (71.3 +/- 3.9 mg/dl) but were significantly higher (p < 0.01) in the CH group (89.8 +/- 8.1 mg/dl). There was nearly a six-fold significant elevation (p < 0.0025) in the DH group (530.0 +/- 58.0 mg/dl) contrasted to the nondiabetic rats fed the same diet. The results of this study indicate that streptozotocin-diabetic rats fed a high cholesterol diet experience hypercholesterolemia.

The effects of acetylsalicylic acid (ASA), on aortic smooth muscle contractility during hypertension were studied in female SHR and WKY rats. The rats were administered two intraperitoneal injections of 10 mg/kg of ASA per week for three weeks. Twenty four hours after the last injection the aortic smooth muscles were evaluated for generation of active tension in response to KCl, phenylephrine, clonidine and norepinephrine. We report that aortic rings from ASA-treated SHR animals were more responsive than rings from non-treated SHR female rats. ASA treatment of SHR animals restored the contractile response to the level shown by non-treated WKY control female rats. The response from aortic rings of ASA-treated SHR to KCl, phenylephrine and clonidine was essentially similar to the response of rings from non-ASA-treated WKY control female rats. We did not observe any decrease in the systolic blood pressure during the ASA treatment in SHR female rats. These results suggest that acetylsalicylic acid modulates aortic smooth muscle contractility either through the metabolites of arachidonic acid or through alpha-adrenoceptors.