Conversion of arachidonate to prostanoids by lung microsomes from rats fed varying amounts of vitamin E

This study was conducted to investigate the effect of dietary vitamin E on prostaglandin (PG) synthesizing activities in the rat lung. Five groups of weanling male rats were fed for 9 wk a vitamin E deficient diet supplemented with 0, 20, 40, 200 and 400 mg-dl-alpha-tocopherol acetate/kg (E0, E20, E40, E200 and E400). Microsomes from lungs of each group were incubated in the presence of [1-14C]-arachidonate. Separation of metabolites was achieved by reversed phase HPLC. Six prostanoids: 6-keto-PGF1 alpha, 6-keto-PGE1, TXB2, PGF2 alpha, PGE2 and PGD2 were eluted isocratically with the solvent system of acetonitrile-water (pH 3.0) (34:66, V/V). Fractions of eluent were collected and the radioactivity of each fraction was determined. The predominant prostanoid synthesized by rat lung microsomes was 6-keto-PGF1 alpha. The specific activity (pmole PG produced/mg protein/min) for the synthesis of 6-keto-PGF1 alpha was 17.6, 29.3, 16.3, 15.3 and 21.2 for the E0, E20, E40, E200 and E400 groups, respectively. Only minor amounts of 6-keto-PGE1, TXB2, PGF2 alpha, PGE2 and PGD2 were synthesized by rat lung microsomes. Although rats fed vitamin E at 20 mg/kg diet showed the highest enzymatic activity for the synthesis of 6-keto-PGF1 alpha, dietary vitamin E had little overall effect on lung microsomal prostanoid biosynthesis.