Cardiac HIF activity after PHD2 inactivation. (A,B) Immunoblot analysis of heart whole-cell extracts from 6-week-old (VHL flox/flox) or 8-week-old (PHD2 flox/flox) mice that did (+) or did not (−) express Cre-ER. Mice were treated with tamoxifen at E17.5 and at 3 weeks of age. (C) Real-time RT-PCR analysis for the indicated mRNAs in hearts from 26- to 33-day old PHD2 flox/flox;CreER (−) and PHD2 flox/flox;Cre-ER (+) mice after treatment with tamoxifen at E17.5 and at 3 weeks of age. *P < .05; **P < .01. Error bars indicate 1 SD.