Transgenic hearts overexpress 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2) protein and have elevated fructose-2,6-bisphosphate (Fru-2,6-P2). A: for the Western blot, cardiac protein was analyzed using rabbit anti-rat liver PFK-2 antibody. Extracts from 3 Mk1 hearts are shown. Similar results were obtained in all Mk transgenic lines. B: for the measurement of Fru-2,6-P2, hearts were extracted with 50 mM NaOH and estimated using pyrophosphate-dependent fructose-6-phosphate 1-phosphotransferase. Transgenic Fru-2,6-P2 values were significantly higher than those in FVB hearts (*P < 0.01 by ANOVA). No significant differences were obtained within Mk groups. The number of animals used were 4 FVB, 4 Mk1, 4 Mk2, and 3 Mk5 mice.