Search results for "Thromboxane"
showing 10 items of 64 documents
Gathering of aging and estrogen withdrawal in vascular dysfunction of senescent accelerated mice.
2010
The aim of this work was to characterize a mouse model of experimental menopause and cardiovascular aging that closely reflects menopause in women. Senescence accelerated mouse (SAM)-Resistant type 1 (SAMR1, n=30) and SAM-Prone type 8 (SAMP8, n=30) were separated at 5months of age into three groups: 1) sham-operated (Sham); 2) ovariectomized (Ovx); and 3) ovariectomized chronically-treated with estrogen (Ovx+E2). Contractile responses to KCl (60mM) and thromboxane A(2) were greater in aorta from SAMP8 mice compared with SAMR1 in all groups. Neither ovariectomy nor estrogen replacement modified the contractile responses from SAMR1 mice. Conversely, in Ovx SAMP8 the increased maximal contract…
Receptor Binding Properties of the New and Specific Thromboxane Receptor Antagonist Bay U 3405
1992
Human platelet membranes were used to characterize the receptor binding properties of the specific thromboxane receptor antagonist 3H-SQ 29548 and the displacement of 3H-SQ 29548 from its binding site by the new thromboxane receptor antagonist Bay u 3405. The specific binding of 3H-SQ 29548 was saturable with an association rate constant of 1 x 10(-11) mol-1 min-1 and a dissociation rate constant of 0.032 min-1. Nonspecific binding of 3H-SQ 29548 was below 10%. When Scatchard plot analysis was performed on equilibrium saturation binding the kD was 69 nmol/l and the Bmax was calculated as 3.9 pmol/mg membrane protein. 3H-SQ 29548 was dose dependently displaced from its binding site by additi…
Different metabolic behavior of long-chain n-3 polyunsaturated fatty acids in human platelets.
1988
Abstract Whereas numerous studies deal with the effects and metabolism of eicosapentaenoic acid (20:5( n −3)) in platelets, very few concern docosahexaenoic acid (22:6( n −3)), although both acids are consumed in equal amounts from most fish fat. The present paper reports the modulation of 22:6( n −3) oxygenation as well as that of endogenous arachidonic acid (20:4( n −6)) in 22:6( n −3)-rich platelets. Like the oxygenation of 20:5( n −3), the lipoxygenation of 22:6( n −3) occurred at a low level when incubated alone, but was markedly increased in the presence of 20:4( n −6), suggesting a similar peroxide tone dependency. 20:5( n −3) could not replace 20:4( n −6) in the increasing 22:6( n −…
Enhanced Lipid Peroxidation and Platelet Activation in the Early Phase of Type 1 Diabetes Mellitus
2003
Background— To investigate early events possibly related to the development of diabetic angiopathy, we examined whether 8-iso-prostaglandin F 2α (8-iso-PGF 2α ) formation, a marker of in vivo oxidant stress, is altered in different stages of type 1 diabetes (T1DM) and whether it correlates with the rate of thromboxane (TX) A 2 biosynthesis, a marker of in vivo platelet activation. We also investigated the relationship between inflammatory markers and F 2 -isoprostane formation in this setting. Methods and Results— A cross-sectional study was performed in 23 insulin-treated patients aged <18 years with new-onset T1DM (≤6 weeks, group A), matched for age and gender with 23 patients with s…
Vascular aging in women: is estrogen the fountain of youth?
2012
Aging is a physiological process associated with structural and functional changes in vasculature, including endothelial dysfunction, arterial stiffening and remodeling, impaired angiogenesis, and defective vascular repair, and with an increasing prevalence of atherosclerosis. The risk of cardiovascular disease differs between men and women, remaining lower in women during their fertile years and reaching values similar to their male peers after menopause. Menopause is marked by the loss of endogenous estrogen production. Therefore, estrogens have been implicated in premenopausal protection from cardiovascular disease, an assumption supported by experimental and some clinical studies, where…
Acute methionine load‐induced hyperhomocysteinemia enhances platelet aggregation, thromboxane biosynthesis, and macrophage‐derived tissue factor acti…
1997
A moderate elevation of plasma homocysteine is a risk factor for atherosclerosis and arterial and veinous thrombosis. However, the mechanisms leading to vascular disorders are poorly understood because studies that have investigated the potential atherothrombogenicity of hyperhomocysteinemia in vivo are scarce. Using a rat model, we were the first to show that dietary folic acid deficiency, a major cause of basal hyperhomocysteinemia, is associated with enhanced macrophage-derived tissue factor and platelet activities. We proposed that an homocysteine-induced oxidative stress may account for this hypercoagulable state. To determine the true thrombogenicity of moderate hyperhomocysteinemia a…
Thromboxane biosynthesis, neutrophil and coagulative activation in type IIa hypercholesterolemia
1995
SummaryThromboxane (Tx) A2 biosynthesis is enhanced in the majority of patients with type IIa hypercholesterolemia. Because blood clotting activation is an important component of the inflammatory response, involved in the initiation and progression of atherosclerotic plaques, we have investigated TxA2 biosynthesis, neutrophil activation and thrombin generation in 24 patients with type IIa hypercholesterolemia.Urinary 11-dehydro-TxB2, was significantly higher (p =0.0001) in patients than in 24 sex- and age matched healthy subjects. Similarly, prothrombin fragment 1+2 (F1+2), thrombin-antithrombin III complexes and plasma elastase were significantly higher in patients than incontrols. Urinary…
Cerebral protection against ischemia by locomotor activity in gerbils. Underlying mechanisms.
1995
Background and Purpose A previous communication of this laboratory demonstrated reduced mortality and neuronal damage by spontaneous locomotor activity preceding forebrain ischemia in Mongolian gerbils. The present experiments seek to elucidate potential mechanisms of protection by measurement of cerebral blood flow, cerebral tissue conductance as an indicator of ischemic cell swelling, and the cerebral release of eicosanoids. Methods Gerbils were maintained either in conventional cages (nonrunners) or with free access to running wheels (runners) for 2 weeks preceding 15 minutes of forebrain ischemia. During ischemia and 2.5 hours of reperfusion, cerebral tissue conductance was determined …
Progestogens reduce thromboxane production by cultured human endothelial cells.
2011
Objectives Progestogens have been poorly studied concerning their roles in endothelial physiology. Prostanoids are vasoactive compounds, such as thromboxane A2, a potent vasoconstrictor, and prostacyclin, a vasodilator. We examined the effects of two progestogens used clinically, progesterone and medroxyprogesterone acetate, on thromboxane A2 production by cultured human umbilical vein endothelial cells (HUVEC) and investigated the role of progesterone receptors and the enzymes involved in production of thromboxane A2 and prostacyclin. Methods Cells were exposed to 1‐100 nmol/l of either progesterone or medroxyprogesterone acetate, and thromboxane A2 production was measured in culture mediu…
Platelet Function During Ticlopidine and Eicosapentaenoic Acid Administration in Patients with Coronary Heart Disease
2010
Antiplatelet drugs have been reported to be useful in unstable angina. This study was designed to investigate the effects of simultaneous administration of ticlopidine and eicosapentaenoic acid (EPA) on platelet function in coronary heart disease (CHD) patients. Ticlopidine significantly reduced platelet aggregation induced by ADP and collagen with no effect on arachidonate metabolism. The aggregation responses to collagen, ADP and arachidonate were not altered significantly by EPA (as fish oil) intake whereas thromboxane A(2) formation was reduced, but not completely inhibited. Combined therapy seems to achieve a more marked degree of inhibition of aggregation together with a fall in the u…