(A) Relative expression of mRNA was measured by expression microarray (Affymetrix Rat Genome Array 230 2.0). Spatially, mRNA in different zones of growth plate of 1 wk old rats was compared. Temporally, mRNA in proliferative zone at 3, 6, 9 and 12 wk old rats was compared. The data was background corrected and normalized using the MAS5 statistical algorithm. *, P < 0.05 compared with the preceding zone; NS, not significant (B) For significant spatial changes, the relative expression of c-Fos, Hif1a, and Atf3 was verified using quantitative real-time PCR. RZ, resting zone; PZ, proliferative zone; HZ, hypertrophic zone.