Effect of ERT on ADA enzyme activity and adenine substrate concentrations. (A) ADA enzyme activity (nmoles/mg/min) was measured in tissues 4 months after GT with 1 month, 4 months, or 0 months ERT (mean ± SEM). (B) Deoxyadenosine concentration (nmoles/mg of protein) in tissues 4 months after GT with 1 month, 4 months, or 0 months ERT (mean ± SEM). (C) Adenosine concentration (nmoles/mg protein) in tissues 4 months after GT with 1 months, 4 months, or 0 months ERT (mean ± SEM). *Significantly lower adenosine levels in ERT-NoGT mice compared with mice in other conditions (P < .05). **Significantly lower adenosine levels in ERT-NoGT compared 200 + 1mERT and 200 + 4mERT (P < .05). ***Significantly lower in 200 + 4mERT compared with 200 + 1mERT.