Abstract
Platelets undergo dramatic cytoskeletal changes following activation. Previous studies have suggested that these changes are related to the conversion of actin from monomeric (G) to the filamentous (F) form. The present study was designed to determine the polymerization state of actin under conditions associated with platelet shape change without aggregation, in the presence and absence of inhibitors of shape change. Cytochalasin D (CD) is an agent which inhibits platelet shape change as well as actin polymerization in vitro. EDTA-treated, gel-filtered platelets were exposed to the experimental conditions described below prior to Triton lysis. G-actin was measured by the DNAse assay of Blikstad et al. Total cellular actin was determined by assay of lysates exposed to guanidine HC1. Results were expressed as % of total actin measurable as G-actin ± SEM as follows: (1)unstimulated 67.5±1.4, n=32, (2)thrombin-stimulated 36.8±1.2, n=25, (3)CD-treated (before thrombin) 62.4±2.1, n=21, (4)CD-treated (after thrombin) 69.4±2.0, n=8, (5)ADP-stimulated 44.0±1.0, n=4, (6)Adenosine-treated (prior to ADP) 63.0±3.1, n=4, (7)CD-treated (prior to ADP) 66.8±5.7, n=4. These findings indicate that platelet actin is reversibly transformed from G-actin to F-actin during shape change. This transformation is blocked both by a drug which competitively inhibits stimulation and shape change (adenosine), and a drug which inhibits actin polymerization and shape change (CD).
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Casella, J., Lin, S. & Zinkham, W. 798 ACTIN UNDERGOES RAPID AND REVERSIBLE POLYMERIZATION ASSOCIATED WITH PLATELET SHAPE CHANGE. Pediatr Res 15 (Suppl 4), 575 (1981). https://doi.org/10.1203/00006450-198104001-00822
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DOI: https://doi.org/10.1203/00006450-198104001-00822