Fig. 4.

Dox-induced increase in serum CK activity. Three-month-old, male mice were given a single i.p. injection of Dox (at 5, 10, or 20 mg/kg; n = 5) or saline (n = 4). Four days after Dox treatment, serum samples were obtained, and CK activity was determined as described in Materials and Methods. The enzyme activity (rate of formation of NADPH) was expressed as U/L, which was calculated as [changes in absorbance per min] × 4180. *, P < 0.05; **, P < 0.01, compared to saline-treated mice of the same strain (Student’s t-test).