title: Generation and degradation of fibrinopeptide A in stored platelet concentrate.
abstract: The levels of fibrinopeptide A (FPA) were measured in samples from stored platelet concentrates (PC) by radioimmunoassay. In 27 standard, citrated PC, the mean FPA was 13.6 ng/ml, which is elevated 5-6X over background levels. This value did not change significantly over a 7-day storage period. Addition of PGE-1 and theophylline resulted in higher initial levels of FPA (18.0 ng/ml) and a pronounced rise during the storage period (to 43.4 ng/ml by day 10). In contrast, addition of a thrombin inhibitor, D-phenylalanyl-L-prolyl-L-arginine chloromethyl ketone-2 HCl (PPACK) or hirudin, resulted in lower initial levels of FPA relative to standard, citrated PC and a slow increase over time. Introduction of exogenous FPA into citrated PC resulted in a predicted elevation of FPA levels followed by a rapid loss of immunoreactivity (t1/2 = 18 h). Addition of PPACK did not affect this fall-off. However, PC prepared and stored in the presence of PGE-1 and theophylline showed a much slower fall-off of exogenous FPA (t1/2 = 38 h). These data indicate that FPA levels in samples from citrated PC represent a dynamic balance between generation and degradation processes and, thus, the data above underestimate the amount of thrombin activity present in stored, citrated PC.
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D001792:Blood Platelets / Q000378:metabolism*; D001793:Blood Preservation; D002951:Citrates / Q000502:physiology; D005340:Fibrinogen / Q000032:analysis*; D005344:Fibrinopeptide A / Q000032:analysis* / Q000378:metabolism; D006801:Humans; D011863:Radioimmunoassay; D013917:Thrombin / Q000032:analysis / Q000037:antagonists & inhibitors
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D002951:Citrates; D005344:Fibrinopeptide A; D005340:Fibrinogen; D013917:Thrombin; C040308:phenylalanyl-prolyl-arginine-chloromethyl ketone