Prostaglandin E1-induced deconsolidation of thrombin-activated platelet aggregates I: ultrastructure-computer image analysis.
We have compared, at an ultrastructural-computer image morphometric level, the relaxation induced by Mg-ethylene-bis-oxyethylenenitrilo-tetracetic acid and prostaglandin E1 on a model of a thrombin-activated platelet aggregate. Mg-ethylene-bisoxyethylenenitrilo-tetracetic acid produced a small increase of 5.0% of the intercellular space over the control levels, and a decrease of 10.0+/-1.3% of the cross-sectional area of the platelets, with no apparent cytoskeletal alterations. In contrast, the prostaglandin El-treated preparation shows a 360% increase in the intercellular space and a decrease of the average platelet cross-sectional area of 30.0+/-2.0% with marked cytoskeletal alterations. We use the term "deconsolidation" to describe this effect. The enlargement of the intercellular space allows the observation of two types of contacts: (1) a type S (segmental) complex, of approximately 200-nm length that maintains a narrow interplatelet gap of 20-30 nm, filled with a dense intercellular material, and (2) a type R (reticular) complex, formed by scant focal regions of the plasma membrane from opposing platelets that are connected through a mesh of fibrillar or granular material contained within a variable-size space. We hypothesize that deconsolidation is caused by fluid loss from the platelets into the intercellular space. As a result, platelet volume decreases and intercellular space increases.
Salganicoff
L
L
Department of Pharmacology, Temple University Medical School, Philadelphia, Pennsylvania 19140, USA. ls23529@astro.ocis.temple.edu
Russo
M A
MA
Sevy
R W
RW
D000527:Alprostadil / Q000494:pharmacology*; D001792:Blood Platelets / Q000166:cytology / Q000648:ultrastructure; D002450:Cell Communication; D002614:Chelating Agents / Q000494:pharmacology; D003593:Cytoplasm / Q000473:pathology; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D003599:Cytoskeleton / Q000648:ultrastructure; D004533:Egtazic Acid / Q000494:pharmacology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D015539:Platelet Activation / Q000187:drug effects*; D010974:Platelet Aggregation / Q000187:drug effects*; D013917:Thrombin / Q000502:physiology*
D002614:Chelating Agents; D004533:Egtazic Acid; D013917:Thrombin; D000527:Alprostadil