To begin to understand the mechanisms regulating O-GlcNAc cycling, we examined the abundance of the O-GlcNAc-cycling enzymes (OGT, OGA, and GFAT2), OGT and OGA activity, and UDP-GlcNAc levels in hearts, either after 20 min of ischemia or after 120 min of reperfusion. The gene discussed is OGT; the disease is ischemia.