Menaquinone-4 increases CYP11A protein levels in I-10 cells. I-10 cells were treated with menaquinone-4 (MK-4) for the indicated time. After the treatment, whole cell extract was prepared, and CYP11A and StAR levels were measured by Western blot analysis (A). Whole cell extracts from the testis of rats fed control (Cont) or MK-4 supplemented (MK-4 sup) diets for 5 weeks were prepared, and CYP11A levels were measured by Western blot analysis (B). Data are represented as mean ± SE (n = 3) normalized to α-tubulin (A) or β-actin levels (B) and expressed as a fold-increase/decrease of values compared to the MK-4 control cells or the control diet group. Values with different letters are significantly different at p < 0.05.