Figure 3: Expression of adenylyl cyclase and G protein subunits in the developing chick heart. Proteins from myocardial membrane preparations derived from different developmental stages of the chick embryo were resolved by SDS-PAGE, transferred to nitrocellulose membranes, and probed with specific antibodies to AC5 isoform and α subunits of Gs and Gi(1,2) proteins. After stripping, the membranes were reprobed with actin antibody to control for differences in protein loading. Representative blots are shown, each of three independently performed experiments (a) and the graphical representation of relative expression levels (means ± SEM) of AC5, Gsα, and Giα normalized to the corresponding expression of actin (b). * Indicates significantly different expression of the individual proteins in samples from ED8, ED12, and ED12 as compared to ED4 ( ).