RESUMO
AIM: Hematopoietic stem cells, especially CD117(pos) cells, have been found to possess a regenerative potential in various tissues, in particular cardiac muscle. However, the characterization of the relevant ion currents of stem cells prior to implantation lacks documentation. Activation of angiotensin II type 2 receptor (AT2 R) can lead to further cell differentiation and receptor auto-expression and might thus influence electrophysiological properties of CD117(pos) stem cells. This study was designed to functionally characterize membrane currents of CD117(pos) cells under normal and AT2 R-stimulated conditions. METHODS: CD117(pos) murine bone marrow stem cells were isolated with MACS technique and stimulated for the AT2 R with angiotensin II and losartan for 3-5 days prior to patch-clamp measurements. RT-PCR was used to determine channel expression. Endothelial properties were analysed with immunocytochemistry and acLDL uptake assay. RESULTS: A well-expressed inward rectifying current (IKir ) was identified in cultured CD117(pos) cells. Furthermore, a ZD 7288 (HCN channel blocker)-sensitive current component was isolated. Voltage-dependent potassium currents and chloride currents were less expressed. A small fraction of cells demonstrated voltage- and time-dependent inward currents. In AT2 R-stimulated cells inward rectifying the hyperpolarization-induced inward currents were slightly attenuated on the translational level but showed increased mRNA expression. Cultured CD117(pos) cells express CD31 and VEGFR-2 and significantly increased the uptake of acLDL. CONCLUSIONS: CD117(pos) cells do not have properties of action potential-generating cells and moderately change their excitability during AT2 R stimulation. Electrophysiological and molecular properties of control and AT2 R-stimulated cells point to a differentiation to vascular endothelial cells. This could increase beneficial vascularization in injured tissues.
Assuntos
Células-Tronco Hematopoéticas/fisiologia , Canais de Potássio Corretores do Fluxo de Internalização/fisiologia , Proteínas Proto-Oncogênicas c-kit/fisiologia , Receptor Tipo 2 de Angiotensina/fisiologia , Angiotensina II/farmacologia , Bloqueadores do Receptor Tipo 1 de Angiotensina II/farmacologia , Animais , Cardiotônicos/farmacologia , Diferenciação Celular/fisiologia , Células Endoteliais/citologia , Células Endoteliais/fisiologia , Coração/fisiologia , Células-Tronco Hematopoéticas/citologia , Técnicas In Vitro , Lipoproteínas LDL/farmacocinética , Losartan/farmacologia , Masculino , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Técnicas de Patch-Clamp , Canais de Potássio Corretores do Fluxo de Internalização/genética , Pirimidinas/farmacologia , RNA Mensageiro/metabolismo , Regeneração/fisiologia , Vasoconstritores/farmacologiaRESUMO
For the determination of traces of boron in iron, low- and high-alloy steels and other materials a direct spectrophotometric method was developed. In this method the absorbance of the boron-Curcumin complex formed in the sample solution is compared with the absorbance of another aliquot of sample solution wherein the boron is rendered inactive with fluoride before the Curcumin is added.
