Microparticles in cardiovascular diseases.

Microparticles are membrane vesicles released from many different cell types. There are two mechanisms that can result in their formation, cell activation and apoptosis. In these two mechanisms, different pathways are involved in microparticle generation.

Isolated microparticles, but not whole plasma, from women with preeclampsia impair endothelium-dependent relaxation in isolated myometrial arteries from healthy pregnant women.

Objective: This study was performed to establish whether microparticles from plasma of women with preeclampsia cause endothelial dysfunction, as described for isolated myometrial arteries in preeclampsia.

Study Design: Myometrial arteries were isolated from biopsy specimens obtained at cesarean delivery from healthy pregnant women (n = 22) and mounted in a wire myograph. Bradykinin concentration-response curves were obtained before and after 1-hour incubation or after overnight incubation with one of the following preparations of plasma from individual women with preeclampsia (n = 16): Whole plasma, microparticle-free plasma, isolated microparticles resuspended in physiologic saline solution or physiologic saline solution.

Endothelial dysfunction in uterine circulation in preeclampsia: can estrogens improve it?

Objective: The purpose of this study was to evaluate whether a 3-hour incubation with 17beta-estradiol will enhance blood flow- and bradykinin-mediated dilatation and alter pressure-induced basal tone in myometrial resistance arteries from women with preeclampsia and to evaluate the role of nitric oxide in the responses that were observed.

Study Design: Blood flow- and bradykinin-mediated dilatation and responses to intraluminal pressure of 60 and 80 mm Hg were compared before and after 3 hours of incubation with 17beta-estradiol (10(-8) mol/L) in isolated myometrial arteries with the pressure myography technique. In separate experiments, the role of nitric oxide on 17beta-estradiol-induced responses was evaluated in the presence of the nitric oxide synthase inhibitor (10(-4) mol/L).

Enhanced coagulation activation in preeclampsia: the role of APC resistance, microparticles and other plasma constituents.

Coagulation activation in pregnancy is further enhanced in preeclampsia. We investigated whether this results from increased thrombin generation by the plasma itself or its cell-derived microparticles. Plasma samples were obtained from preeclamptic, normal pregnant and nonpregnant women (each n = 10).

Microparticle subpopulations are increased in preeclampsia: possible involvement in vascular dysfunction?

Objective: The purpose of this study was to investigate the cellular origin and numbers of circulating microparticles in normal pregnancy and preeclampsia.

Study Design: Plasma samples from 10 women with preeclampsia, from 10 normal pregnant women, and from 10 nonpregnant women matched for age and gestation, were analyzed by flow cytometry.

Results: The total number of circulating microparticles was unaltered in pregnancy and preeclampsia.

Resistance artery smooth muscle function in pregnancy and preeclampsia.

Objective: The purpose of this study was to investigate whether the altered vascular resistance in pregnancy and preeclampsia results from alterations in intrinsic vascular smooth muscle properties or from external influences on vascular smooth muscle function.

Study Design: We studied subcutaneous resistance arteries from women with preeclampsia, from normal pregnant women, and from nonpregnant women, that were obtained during cesarean delivery or gynecologic surgical procedures, in a pressure myograph. Arteries were denervated, and smooth muscle cells were loaded with calcium indicator fura-2.