bongkrekic-acid and 5-5--6-6--tetrachloro-1-1--3-3--tetraethylbenzimidazolocarbocyanine

Coated-platelets are a subset of cells observed during costimulation of platelets with collagen and thrombin. Important characteristics of coated-platelets include retention of multiple alpha-granule proteins and expression of phosphatidylserine on the cell surface. The mitochondrial permeability transition pore (MPTP) is a key step in apoptosis and is suggested to be involved in some forms of platelet activation. The objective of this study was to examine the role of MPTP in the synthesis of coated-platelets.. Flow cytometric analysis of coated-platelet production was used to examine the impact of pharmacological effectors of MPTP formation. Cyclosporin A, coenzyme Q, and bongkrekic acid all inhibit MPTP formation as well as production of coated-platelets. Phenylarsine oxide and diamide, both potentiators of MPTP formation, stimulate coated-platelet synthesis. Atractyloside, another inducer of MPTP formation, does not affect the percentage of coated-platelets synthesized; however, it does increase the level of phosphatidylserine exposed on the surface of coated-platelets.. These findings indicate that MPTP formation is an integral event in the synthesis of coated-platelets. Although the exact function of the MPTP remains to be determined, these data support a growing body of evidence that apoptosis-associated events are vital components of the platelet activation process. Formation of coated-platelets involves a complex set of activation events initiated by dual agonist activation. The mitochondrial permeability transition pore (MPTP) is a key intermediate in apoptosis and has been suggested to impact platelet activation. This report demonstrates that MPTP formation is essential to production of coated-platelets.

Topics: Adult; Apoptosis; Arsenicals; Atractyloside; Benzimidazoles; Blood Platelets; Bongkrekic Acid; Carbocyanines; Collagen; Crotalid Venoms; Cyclosporine; Cytoplasmic Granules; Diamide; Drug Synergism; Flow Cytometry; Fluorescent Dyes; Humans; Ion Channels; Lectins, C-Type; Membrane Lipids; Mitochondrial Membrane Transport Proteins; Mitochondrial Permeability Transition Pore; Phosphatidylserines; Platelet Activation; Thrombin; Thromboplastin; Ubiquinone

The relative magnitude of the inner mitochondrial membrane potential (DeltaPsim) has been suggested to indicate the competence of mammalian gametes and early embryos. This study examined the response of cultured somatic cells and mouse oocytes to inhibitors and conditions that affect DeltaPsim or metabolism, or both, and measured treatment-specific changes in ATP and cytoplasmic free Ca(2+).. During and after treatment, relative DeltaPsim, free Ca(2+), and ATP levels and cortical granule density were determined.. Comparable responses of somatic cells and metaphase II mouse oocytes to experimental manipulations that affect DeltaPsim and metabolism were observed and reversible loss of DeltaPsim was associated with increased intracellular free Ca(2+), which in certain instances resulted in parthenogenetic activation.. The findings support a mitochondrial basis for pericortical J-aggregate fluorescence but not for a direct association between high DeltaPsim and metabolism. The results extend previous findings indicating that high-polarized (high DeltaPsim, JC-1 J-aggregate-forming) mitochondria occur in pericortical domains in mouse and human oocytes and early preimplantation stage embryos and support the notion that this spatial distribution may be related to localized ionic and metabolic regulation.

Topics: Adenosine Triphosphate; Animals; Benzimidazoles; Bongkrekic Acid; Calcimycin; Calcium; Carbocyanines; Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; Cells, Cultured; Cytoplasm; Exocytosis; Fibroblasts; Fluorescent Dyes; Humans; Intracellular Membranes; Ionophores; Membrane Potentials; Metaphase; Mice; Mitochondria; Oligomycins; Oocytes; Temperature