Steady-state fluorescence polarization (FP) of 1,6-diphenyl-1,3,5-hexatriene (dph)-labelled platelets in the presence of bradykinin (bk).

Steady-state fluorescence polarization (FP) decreases, when 1,6-diphenyl-1,3,5-hextriene (dph) labelled platelets are exposed to bradykinin (bk). At pH 8, the dose-response curve is bell-shaped with an optimum bk effect at 10(-7) M. In contrast to the ricinoleic-acid ester of glycerin-polyethyleneglycol, cremophor EL (CEL), bk is no more effective when platelets are pretreated with 10(-5) M p-bromophenacylbromide (B phi B). These results suggest that platelets are target cells for the peptide bk, which induces an FP decrease indirectly by stimulating the release of non-saturated fatty acids in the platelet membrane.