A simple method for estimation of lipoxygenase and cyclo-oxygenase pathways in human platelets--the use of thiobarbituric acid reaction.

To develop a simple method for estimation of platelet lipoxygenase (PLO) and cyclo-oxygenase (PCO) pathways, the arachidonic acid (AA) metabolism of human platelet was investigated under various experimental conditions by the use of the thiobarbituric acid (TBA) reaction and a radioisotope technique. A TBA-reactive substance different from malondialdehyde (MDA) via PCO pathway was detected and shown to be derived from the PLO pathway. Since the optimal pH and time course of its formation were different from those of MDA formation via PCO pathway, PLO and PCO pathways were estimated by quantitating the TBA-reactive substances produced by the incubation of AA either with aspirin-treated platelets or with untreated ones, respectively, each under optimal conditions. Normal values expressed in terms of nmol MDA/10(8) platelets were 1.17 +/- 0.34 (M +/- SD, n = 31) and 0.79 +/- 0.15 (n = 31) for PLO and PCO pathways respectively.