PROSTAt;LANDINS A MASS FRAGMENTOGRAPHIC PROCEDURE FOR THE SIMULTANEOUS DETERMINATION OF HETE AND PGF2c, IN THE CENTRAL NERVOUS SYSTEM L. Sautebin, C. Spagnuolo, C. Galli and G. Galli Institute of Pharmacology and Pharmacognosy, University of Milan, Milan, Italy The metabolic conversion of arachidonic acid to endo peroxides through the activity of a cyclooxygenase and to hydroperoxy (HPETE) and hydroxy (HETE) unsaturated fatty acids through a lipoxygenase has been described in several tissues (l-5). However, no data are available up to now on the presence of the lipoxygenase metabolites in brain. Aim of the present work was to set up a procedure for the simultaneous determination of HETE and of PGF in rat brain cortex. This methodological approach allows2ghe eva- luation of the balance between the two major pathways of arachidonic acid conversion under different physiological and pharmacological conditions. Brain cortical tissues of animals sacrificed by the use of a focussed microwave oven (6) were homogenized, extracted and purified accord- ing to the scheme shown in Fig. 1, and the extracts were analyzed by mass fragmentography (2,7). Deuterated HETE (d8-HETE) added as internal standard was prepared by in- cubation with human platelets of d s -arachidonic acid ob- tained by hydr9genation of 5,8,11, acid (8) with H2 (99.9% 2H). I-eicosatetraynoic The tetraynoic acid and d4 PGF2 were generous gifts of Crinos Company, Italy and upjoffn, Kalamazoo, U.S.A., respectively. HETE was found in rat brain cortex and its levels were of the same order of magnitude of those of PGF (Table 1). HETE levels were also m %sured g after post-decapita- tion ischemia in the rat and compared with those of PGF which are known to increase under this experimental con i- sa tion (9). As shown in Table 1 the concentrations of both compounds were enhanced to the same extent in the ischemic cortex. Thus, stimulation of HETE and PGF2u formation in brain appear to be associated. The biological significance of HETE in tissues is lag gely unknown. However the recent finding (10) that HPETE inhibits Thromboxane A2 (TKA 1 synthase in human platelets, may suggest a similar role 0 Z lipoxygenase products in other tissues, including brain where TKA2 formation from DECliMBER 1978 VOL. 16 NO. 6