Activation of the renin-angiotensin system. Activity of the RAS was measured in cardiac myocytes isolated from wild type (A- C) and AT1a-KO (A, D- E ) mice after 1 wk of diabetes. ANG II (A) was extracted from cardiac myocytes and measured using a competitive ELISA. Angiotensinogen (AGT, B and D) and renin (C and E) expression was measured in control and diabetic (STZ) samples, by real-time RT-PCR and normalized to 18S mRNA. Values are expressed as the fold change compared to control ± SEM. *P < 0.05 vs. control.