(A) Total MMP-9 in plasma at 7 weeks and endogenous active MMP-9 at 13 weeks exposure. Values are shown as mean ± STD, † p<0.1, ‡ p<0.05. For 7 weeks groups n = 5, for 13 weeks groups n = 6. (B) Comparison of endogenous active MMP-9 in plasma after 7 and 13 weeks exposure. Values are shown as mean ± STD, * p<0.01. For 7 weeks groups n = 5, for 13 weeks groups n = 6. (C) Gelatin zymography of pooled plasma taken after 5 to 20 weeks exposure, stained gel is shown along with inversion image and corresponding densitometry analysis of the most prominent band (indicated with arrow). For pooling plasma n = 4 at 5 weeks, n = 6 at 13 weeks, and n = 5 for remaining time points.