Int. J. Environ. Res. Public Health 2012, 9 486 [compare Figure 10(D) with Figure 10(C)]. Similarly, cells incubated with 10 µM As3+ for 24 h exhibited a decrease in α and β tubulins and those MAPs sensitive to nocodazole [arrowheads in Figure 10(B)] in comparison to the control in the absence of As3+ treatment [Figure 10(A)]. Note that the internal control of actin was not significantly changed. Quantitative densitometric analysis indicated that the integrated intensities of MAPs 50/6.5, 53/6.5, 60/6.4, 62/6.3 and 86/6.5 were decreased to 44%, 49%, 15%, 48%, and 12% of the control, respectively. In view of the critical role of MAPs in the MT stability [29], decreases in the levels of several MAPs would contribute to MT instability favoring their disassembly. Figure 9. Taxol antagonistic effects on As3+-induced MT injury. Growth–arrested RFL6 cells on coverslips were treated with As3+, NEM, or their combinations with taxol for 24 h, and then stained with an anti-β tubulin antibody-FITC to visualize MTs. (A) control cells; (B) cells treated with 20 µM taxol; (C) cells treated with 20 µM As3+; (D) cells treated with 20 µM As3+ + 20 µM taxol; (E) cells treated with 25 µM NEM; (F) cells treated with 25 µM NEM + 20 µM taxol.