Induction of VEGF expression in ischemic hearts by the MLCVEGF vector. Expression of human VEGF mRNA was shown as the relative threshold of VEGF and LacZ mRNA and was calculated based on the threshold cycle (CT). ΔCT, relative threshold cycle; Δ{ΔCT(VEGF-LacZ)} = ΔCTVEGF-ΔCTLacZ where ΔCTVEGF = CTVEGF-CTmHPRT; ΔCTLacZ = CTLacZ-CTmHPRT. The y axis indicates the relative threshold cycles. The larger the number, the more cycles were required to reach the threshold, indicating lower gene expression. The relative thresholds for CMVVEGF were similar for normal heart (1.50 ± 0.80) and ischemic hearts (1.51 ± 0.79), whereas the relative threshold for MLCVEGF-injected hearts decreased from 3.11 ± 0.38 (normal hearts) to 2.31 ± 0.34 (ischemic heart), indicating a 74% increase of VEGF expression in ischemic hearts compare with normal hearts.