title: Rapid aequorin loading into platelets in the presence of DMSO--characteristics of the responses (changes in light transmission and in calcium) to various agonists.
abstract: We have looked at different parameters which could modify platelet behaviour during and after aequorin loading in the presence of DMSO. There is a decreased platelet reactivity in response to ADP, PAF and A-23,187 which appears to be mainly due to the exposure to EGTA during washing and loading and the 1 ml volume of the test suspension. All the studied agonists (including PMA) which elicit aggregation are able to induce an intracellular Ca2+ change detected with the aequorin probe. By contrast, epinephrine alone induces neither aggregation nor Ca2+ rise, but potentiates the responses to ADP. Different consecutive phases in Ca2+ changes after stimulation with ADP, PMA and A-23,187 can be evidenced. In the presence of external Ca2+, the second component of the Ca2+ change evoked with ADP is dependent on aggregation and the subsequent TXA2 synthesis. When the external medium is Ca2+ depleted, the two Ca2+ peaks induced by ADP disappear whereas a Ca2+ rise persists (endogenous mobilization) with the other agonists, being independent of TXA2 and ADP release. Ca2+ mobilization parallels activation with A-23,187 but not with low concentrations of thrombin.
authors.affiliation: Central Laboratory of Hematology, Hôtel-Dieu Hospital, Paris, France.
authors.forename: F
authors.initials: F
authors.lastname: Potevin
authors.forename: T
authors.initials: T
authors.lastname: Lecompte
authors.forename: R
authors.initials: R
authors.lastname: Favier
authors.forename: M
authors.initials: M
authors.lastname: Samama
mesh_terms: D000331:Aequorin; D001792:Blood Platelets; D002118:Calcium / Q000097:blood*; D004121:Dimethyl Sulfoxide; D006801:Humans; D008027:Light; D013997:Time Factors
chemical_list: D000331:Aequorin; D002118:Calcium; D004121:Dimethyl Sulfoxide