Figure 4.

Upregulation of AK isoforms in rat extraocular muscle. (A) Total AK activity in EDL and extraocular muscles (n = 9, P > 0.35). (B) Relative abundance of mRNAs for four AK isoforms in extraocular muscle by quantitative PCR. Each sample includes pooled muscles from 4 rats. Data are mean -fold differences (3–4 samples) in AK isoform expression and normalized to EDL muscle = 1.0, shown by the horizontal reference line. The abundance of AK1 and AK2 mRNAs was not significantly different in extraocular and EDL muscles (black bars). AK3 and AK4 are expressed at significantly higher levels in extraocular muscle (13.5- and 16.2-fold greater than EDL, respectively).