Electrorotation measurements of diamide-induced platelet activation changes.
Electrorotation is a special dielectric spectroscopic technique capable of measuring the polarizability of single platelets. The rotational speed of the particles is recorded as a function of the frequency of the applied rotating electric field. As previously shown, the speed of electrorotation in the range of the first characteristic frequency (anti-field rotation) decreased upon activation and was correlated with [14C]serotonin release and an increase of the TMA-DPH-induced fluorescence. Diamide upon activation and was correlated with [14C]serotonin release and an increase of the TMA-DPH-induced fluorescence. Diamide incubation induced morphological changes in control platelets. These changes were accompanied by a shift of the first characteristic frequency of electrorotation toward higher values and a parallel increase of the anti-field rotation. This was explained by a decrease of membrane conductivity and by the changed polarizability of platelet interior due to the observed internal platelet structure changes. Diamide inhibited activation assessed by both electrorotation and TMA-DPH fluorescence in the case of all activators except the ionophore A 23187. Because diamide largely inhibited the A 23187-induced serotonin release, it was concluded that, despite the diamide treatment, the direct increase of cytoplasmic Ca2+ was still able to induce membrane conductivity changes accessible by electrorotation, but this did not complete the final release step of the activation process.
Egger
M
M
Physiologisches Institut, Universität Zürich, Switzerland.
Donath
E
E
D055592:Biophysical Phenomena; D001703:Biophysics; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D000001:Calcimycin / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D003958:Diamide / Q000494:pharmacology*; D004161:Diphenylhexatriene / Q000031:analogs & derivatives; D004560:Electricity; D005456:Fluorescent Dyes; D006801:Humans; D066298:In Vitro Techniques; D008854:Microscopy, Electron; D008954:Models, Biological; D015539:Platelet Activation / Q000187:drug effects* / Q000502:physiology*; D012399:Rotation; D012701:Serotonin / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013057:Spectrum Analysis / Q000379:methods
D005456:Fluorescent Dyes; D003958:Diamide; D004161:Diphenylhexatriene; D012701:Serotonin; D000001:Calcimycin; C033628:1-(4-(trimethylamino)phenyl)-6-phenylhexa-1,3,5-triene