TY - JOUR
T1 - Observations on the Effects of Cytochalasin B and Cytochalasin D on ADP- and Chymotrypsin-Treated Platelets (41776)
AU - Peerschke, Ellinor I.B.
PY - 1984/1
Y1 - 1984/1
N2 - Cytochalasin B has been reported to inhibit fibrinogen binding and aggregation of rabbit platelets in response to ADP. The present study was designed to ascertain whether cytochalasins B and D inhibit aggregation by interfering with the exposure of fibrinogen receptors or more directly by inhibiting binding to available receptors. Aspirin-treated, washed, human platelets stimulated with ADP or chymotrypsin were used for these studies. Neither cytochalasin B nor D significantly inhibited the binding of fibrinogen to chymotrypsin-treated platelets when these agents were added to platelet suspensions before (16 ± 8% (mean ± SD) inhibition, N = 8), or after (15 ± 10% inhibition, N = 13) chymotrypsin treatment, i.e., before or after fibrinogen receptor exposure. This apparent lack of cytoskeletal involvement was consistent with the observation that chymotrypsin-treated platelets were unable to retract reptilase-induced fibrin clots, an activity that was restored by adding ADP. In contrast, incubating platelets with either cytochalasin B or D for 30 min before or after stimulation with ADP decreased fibrinogen binding by 42 ± 16% (N = 13) and 27 ± 11% (N = 8), respectively, compared to DMSO-treated controls. Platelets stimulated with ADP and incubated with DMSO for 30 min, however, became refractory and aggregated poorly in response to a second dose of ADP. In comparison, platelets stimulated with ADP, but incubated with cytochalasin B or D, aggregated more extensively when stimulated by a second dose of ADP despite diminished fibrinogen binding. The data suggest (1) microfilament polymerization is important not only for the exposure of fibrinogen receptors by ADP, but also for preserving the ability of exposed receptors to bind fibrinogen, (2) exposure of fibrinogen receptors by chymotrypsin is not accompanied by significant cytoskeletal activation, and (3) cytochalasins may impart partial protective effects against the development of ADP-induced refractoriness.
AB - Cytochalasin B has been reported to inhibit fibrinogen binding and aggregation of rabbit platelets in response to ADP. The present study was designed to ascertain whether cytochalasins B and D inhibit aggregation by interfering with the exposure of fibrinogen receptors or more directly by inhibiting binding to available receptors. Aspirin-treated, washed, human platelets stimulated with ADP or chymotrypsin were used for these studies. Neither cytochalasin B nor D significantly inhibited the binding of fibrinogen to chymotrypsin-treated platelets when these agents were added to platelet suspensions before (16 ± 8% (mean ± SD) inhibition, N = 8), or after (15 ± 10% inhibition, N = 13) chymotrypsin treatment, i.e., before or after fibrinogen receptor exposure. This apparent lack of cytoskeletal involvement was consistent with the observation that chymotrypsin-treated platelets were unable to retract reptilase-induced fibrin clots, an activity that was restored by adding ADP. In contrast, incubating platelets with either cytochalasin B or D for 30 min before or after stimulation with ADP decreased fibrinogen binding by 42 ± 16% (N = 13) and 27 ± 11% (N = 8), respectively, compared to DMSO-treated controls. Platelets stimulated with ADP and incubated with DMSO for 30 min, however, became refractory and aggregated poorly in response to a second dose of ADP. In comparison, platelets stimulated with ADP, but incubated with cytochalasin B or D, aggregated more extensively when stimulated by a second dose of ADP despite diminished fibrinogen binding. The data suggest (1) microfilament polymerization is important not only for the exposure of fibrinogen receptors by ADP, but also for preserving the ability of exposed receptors to bind fibrinogen, (2) exposure of fibrinogen receptors by chymotrypsin is not accompanied by significant cytoskeletal activation, and (3) cytochalasins may impart partial protective effects against the development of ADP-induced refractoriness.
UR - http://www.scopus.com/inward/record.url?scp=0021350807&partnerID=8YFLogxK
U2 - 10.3181/00379727-175-41776
DO - 10.3181/00379727-175-41776
M3 - Article
C2 - 6694966
AN - SCOPUS:0021350807
SN - 0037-9727
VL - 175
SP - 109
EP - 115
JO - Experimental Biology and Medicine
JF - Experimental Biology and Medicine
IS - 1
ER -