Effects of glycoprotein Ⅱb/Ⅲa antagonists and chloride channel blockers on platelet cytoplasmic free calcium

Platelet activation plays an important role in thrombosis. Platelet glycoprotein Ⅱ b/Ⅲ a （ GPⅡ b/Ⅲ a ） is the receptor of fibrinogen. Platelet cross-linking with fibrinogen through GP Ⅱ b/Ⅲ a is the process of thrombosis. Ca^2＋ is an important intracellular second messenger in platelet activation. It has been reported that GP Ⅱ b/Ⅲ a receptors were involved in the calcium influx of activated platelet, and GP Ⅱ b/Ⅲ a receptor had characteristics of calcium channel or an adjacent calcium channel.

Functional Characteristics and Molecular Identification of Swelling-activated Chloride Conductance in Adult Rabbit Heart Ventricles

Outwardly rectifying swelling-activated chloride conductance （ICl, Swell） in rabbit heart plays a critical role in cardioprotection following ischemic preconditioning （IP）. But the functional characterization and molecular basis of this chloride conductance in rabbit heart ventricular myocytes is not clear. Candidate chloride channel clones （e.g. ClC-2, ClC-3, ClC-4 and ClC-5） were determined using RT-PCR and Western blot analysis.Whole cell ICl,Swell was recorded from isolated rabbit ventricular myocytes using patch clamp techniques during hypo-osmotic stress. The inhibitory effects of 4,4＇ isothiocyanato-2,2-disulfonic acid （DIDS）, 5-nitro-2（3-phenylroylamino） benzoic acid （NPPB） and indanyloxyacetic acid 94 （LAA-94） on ICl,Swell were examined. The expected size of PCR products for ClC-2, ClC-3 and ClC-4 but not for ClC-5 was obtained. ClC-2 and ClC-3 expression was confirmed by automated fluorescent DNA sequencing. RT-PCR and Western blot showed that ClC-4 was expressed in abundance and ClC-2 was expressed at somewhat lower levels. The biological and pharmacological properties of ICl,Swell, including outward rectification, activation due to cell volume change, sensitivity to DIDS, LAA-94 and NPPB were identical to those known properties of ICl,Swell in exogenously expressed systems and other mammals hearts. It was concluded that ClC-3 or ClC-4 might be responsible for the outwardly rectifying part of ICl,Wwell and may be the molecular targets of cardioprotection associated with ischemic preconditioning or hypo-osmotic shock.

Involvement of regulatory volume decrease in the migration of nasopharyn-geal carcinoma cells

The transwell chamber migration assay and CCD digital camera imaging techniques were used to investigate the relationship between regulatory volume decrease (RVD) and cell migration in nasopharyngeal carcinoma cells (CNE-2Z cells). Both migrated and non-migrated CNE-2Z cells, when swollen by 47% hypotonic solution, exhibited RVD which was inhibited by extracellular application of chloride channel blockers adenosine 5’-triphosphate (ATP), 5-nitro-2-(3- phenylpropylamino) benzoic acid (NPPB) and tamoxifen. However, RVD rate in migrated CNE-2Z cells was bigger than that of non-migrated cells and the sensitivity of migrated cells to NPPB and tamoxifen was higher than that of non- migrated cells. ATP, NPPB and tamoxifen also inhibited migration of CNE-2Z cells. The inhibition of migration was positively correlated to the blockage of RVD, with a correlation coefficient (r) = 0.99, suggesting a functional relation- ship between RVD and cell migration. We conclude that RVD is involved in cell migration and RVD may play an important role in migratory process in CNE-2Z cells.