Figure 7. Protease activity within the seminiferous tubule fluid (STF) of control rats (black bars) and rats administered testosterone/estradiol (TE) for 56 days (gray bars). Each STF sample was diluted 1:5 with phosphate-buffered saline (PBS) and incubated for 0-30 minutes as described in "Materials and Methods." The 10-, 20-, and 30-minute time points were normalized to the 0-time point, which was given the numerical value of 1.0. Represented is trinitrobenezenesulfonic acid (TNBSA)-labeled protein as measured by the absorbancy at 450 nm in comparison to the 0-time point. Each time point represents the mean SEM (n = 3) from 3 independent treatment groups. a—statistically different from the control value.