METABOLISM OF THE CELL DIFFERENTIATING AGENT 1-ALPHA,25(OH)(2)-16-ENE-23-YNE VITAMIN-D-3 BY LEUKEMIC-CELLS

The metabolism of 1 alpha,25(OH)(2)D-3 and 1 alpha,25(OH)(2)-16-ene-23 -yne-D-3 is examined by in vitro incubation of the steroid hormones wi th WEHI-3 myeloid leukemia cells. Two experimental systems were used t o evaluate the metabolism of each compound: (a) a double label incubat ion was performed to determine both the propensity for metabolism of e ach analog and the in vitro half-life of the analogs; and (b) separate single label incubations were performed to determine the metabolite p rofile derived from each of the analogs. The double label WEHI-3 cell incubation with 25 nM [23,24(3)H]1 alpha,25(OH)(2)D-3 and 25 nM [25(14 )C]1 alpha,25(OH)(2)-16-ene-23-yne-D-3 produced a single comigrating m etabolite of higher polarity from each of the parent compounds in a gr adient HPLC chromatogram. The half-life of each analog determined from this in vitro incubation was 6.9 and 6.7 h for 1 alpha,25(OH)(2)D-3 a nd 1 alpha,25(OH)(2)-16-ene-23-yne-D-3, respectively. Individual incub ations of 1 alpha,25(OH)(2)D-3 yielded a metabolite that comigrates wi th 1 alpha,24,25(OH)(2)D-3 standard in each of three independent HPLC separations. Individual incubations with [25(14)C]1 alpha,25(OH)(2)-16 -ene-23-yne-D-3 generated multiple metabolites, which are resistant to degradation as evaluated by intermediate build-up, are of increasing polarity and do not comigrate with the 1 alpha,24,25(OH)(3)D-3 standar d. From these studies it is determined that 1 alpha,25(OH)(2)-16-ene-2 3-yne-D-3 is metabolized differently but not preferentially compared t o 1,25(OH)(2)D-3 in myelogenous leukemia cells. (C) 1996 Elsevier Scie nce Ltd.