Figure 5.

Ventricular expression of cardiac G_i. (A) Gα_i2 mRNA was not detectable in knockout mice on either wild-type or β₁-transgenic background and expressed at wild-type level in mice only transgenic for the β₁-adrenoceptor. (B) Gα_i3 mRNA expression was significantly increased compared with wild-type mice in animals lacking Gα_i2 on both a wild-type and β₁-transgenic background, respectively. The number of animals used for qPCR analysis was 3–4 for each genotype. Age range of examined mice was 302 ± 4 days. Asterisks indicate significant differences compared with mRNA expression levels of age-matched wild-type mice in an REST^® analysis (*P < 0.05, **P < 0.01). (C) Representative immunoblots for the Gα_i2 protein in ventricle homogenates. The Gα_i2 protein was absent in Gα_i2^−/− and β₁-tg/Gα_i2^−/− mice. (E) Statistical analysis of Gα_i2 expression levels. (D) Representative immunoblot for the Gα_i3 protein in ventricle homogenates. To verify Gα_i3 antibody specificity, Gα_i3-deficient ventricle homogenates were loaded in addition. (F) Statistical analysis of Gα_i3 expression levels. A significant up-regulation of Gα_i3 protein levels was detectable in Gα_i2^−/− and β₁-tg/Gα_i2^−/− mice. For western blots, individual homogenates from three animals per genotype were analysed in 3–4 independent experiments. β-Actin was used to demonstrate equal loading of the gels. Asterisks indicate significant differences in Bonferroni post-tests following ANOVA (*P < 0.05; **P < 0.01).