TY - JOUR
T1 - The effects of mepacrine and p-bromophenacyl bromide on arachidonic acid release in human platelets
AU - Hofmann, Sandra L.
AU - Prescott, Stephen M.
AU - Majerus, Philip W.
N1 - Funding Information:
i This research supported by Grants HLBI 14147 (Specialized Center in Thrombosis), HL 07088, and I-IL 16634 from the National Institutes of Health, and in part by National Institutes of Health Research Service Award, GM 07200, Medical Scientist, from the National Institute of General Medical Sciences. ‘Author to whom all correspondence should be addressed.
PY - 1982/4/15
Y1 - 1982/4/15
N2 - Two inhibitors of thrombin-stimulated arachidonic acid release from platelets, p-bromophenacyl bromide and mepacrine, were examined for their ability to inhibit the phospholipase C-diglyceride lipase pathway. This pathway involves hydrolysis of phosphatidylinositol to diglyceride, followed by release of arachidonate from diglyceride, and has been proposed as an alternative or addition to phospholipase A2 as a mechanism for arachidonate release. p-Bromophenacyl bromide, a potent alkylating agent, was shown to cause a time-dependent inhibition of phosphatidylinositol-specific phospholipase C activity in crude platelet extracts; the inhibition was >90% after 15 min incubation with 100 μm p-bromophenacyl bromide. However, p-bromophenacyl bromide was also shown to destroy about one-half of the titratable sulfhydryl groups in whole platelets under similar conditions. The lack of specificity of p-bromophenacyl bromide was further demonstrated by our finding that thrombin-stimulated serotonin release was also inhibited by conditions inhibiting arachidonate release and that diglyceride lipase activity was decreased by higher levels of p-bromophenacyl bromide. Mepacrine was found to inhibit the activity of phosphatidylinositol-specific phospholipase C and had a greater effect at low substrate concentrations. The loss of [14C]arachidonate from both endogenous phosphatidylinositol and phosphatidylcholine in intact platelets was also inhibited. Thrombin-stimulated serotonin release was impaired by mepacrine also but only at a concentration 10-fold greater than that required to prevent arachidonate release. Thus we have shown that these two agents which inhibit arachidonate release are inhibitors of the phosphatidylinositol-specific phospholipase C-diglyceride lipase pathway. The multiple effects produced by both compounds limit their utility as agents to examine the source and mechanism of arachidonate release.
AB - Two inhibitors of thrombin-stimulated arachidonic acid release from platelets, p-bromophenacyl bromide and mepacrine, were examined for their ability to inhibit the phospholipase C-diglyceride lipase pathway. This pathway involves hydrolysis of phosphatidylinositol to diglyceride, followed by release of arachidonate from diglyceride, and has been proposed as an alternative or addition to phospholipase A2 as a mechanism for arachidonate release. p-Bromophenacyl bromide, a potent alkylating agent, was shown to cause a time-dependent inhibition of phosphatidylinositol-specific phospholipase C activity in crude platelet extracts; the inhibition was >90% after 15 min incubation with 100 μm p-bromophenacyl bromide. However, p-bromophenacyl bromide was also shown to destroy about one-half of the titratable sulfhydryl groups in whole platelets under similar conditions. The lack of specificity of p-bromophenacyl bromide was further demonstrated by our finding that thrombin-stimulated serotonin release was also inhibited by conditions inhibiting arachidonate release and that diglyceride lipase activity was decreased by higher levels of p-bromophenacyl bromide. Mepacrine was found to inhibit the activity of phosphatidylinositol-specific phospholipase C and had a greater effect at low substrate concentrations. The loss of [14C]arachidonate from both endogenous phosphatidylinositol and phosphatidylcholine in intact platelets was also inhibited. Thrombin-stimulated serotonin release was impaired by mepacrine also but only at a concentration 10-fold greater than that required to prevent arachidonate release. Thus we have shown that these two agents which inhibit arachidonate release are inhibitors of the phosphatidylinositol-specific phospholipase C-diglyceride lipase pathway. The multiple effects produced by both compounds limit their utility as agents to examine the source and mechanism of arachidonate release.
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U2 - 10.1016/0003-9861(82)90300-9
DO - 10.1016/0003-9861(82)90300-9
M3 - Article
C2 - 6807207
AN - SCOPUS:0020366861
SN - 0003-9861
VL - 215
SP - 237
EP - 244
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
IS - 1
ER -