UNLABELLEDTo investigate the regulatory effects of epimedium flavonoids (EF) on adrenocortical regeneration in rats with inhibited hypothalamic-pituitary-adrenal (HPA) axis.

METHODSCell distribution in cell cycle and cell apoptotic rate were measured with PI stain and flow-cytometry; apoptosis cells were showed by in situ terminal-deoxynucleotidyl transferase-mediated deoxy-uridine triphosphate-fluorescene nick end labeling assay (TUNEL), and the genome-wide gene mRNA expression was detected by oligonucleotide microarrays.

RESULTSCompared to the normal control, adrenal cells isolated from the HPA axis inhibited model group were arrested in Go/GI phase, and showed a higher apoptotic rate (P < 0.05). After treated with EF, cells in G0/G1 phase decreased and those in G2/M phase increased (P < 0.01), and the elevated apoptotic rate reduced significantly (P < 0.05). TUNEL assay showed the number of apoptotic cells per section was 4.67 1.53 in the normal control group, 70.67 +/- 9.29 in the model group, and 18.67 +/- 7.64 in the EF-treated group respectively (n=3). Gene expressions in adrenal were mostly restrained in the model group, including 7 cytocycle promoting genes, including V-ras, V-jun, etc., while after treatment with EF, 6 cytocycle promoting genes, 1 anti-apoptotic gene, and genes that closely related with adrenocortical regeneration as IGF-II and FGF7 and their receptors, as well as 7 steroid biosynthesis participated genes were all up-regulated. Conclusion EF can accelerate adrenocortical cell proliferation, inhibit its apoptosis, and promote steroid biosynthesis so as to enhance adrenocortical regeneration in HPA axis inhibited rats, which may contribute to the beneficial effects of EF in protecting adrenocortical function during glucocorticoid withdrawal.