Figure 3.

Preaddition of FKBP12.6 prevents the inhibition of rabbit skeletal RyR1 by FKBP12. (A) A representative diary plot of RyR1 Po changes following preincubation with 200 nM FKBP12.6 and subsequent addition of 500 nM FKBP12 (incubation periods are shown by the bars). Control solutions contained 10 μM cytosolic Ca²⁺ as the sole channel activator. Subsequent addition of 500 nM FKBP12 did not override the activating effects of FKBP12.6. After washout of the cis chamber, Po was not completely reversed to control values. (B) Bar chart showing the mean Po data for control, preaddition of 200 nM FKBP12.6, subsequent addition of 500 nM FKBP12, and washout to control solutions (SE; n = 4). Pretreatment with picomolar levels of FKBP12.6 (C) or FKBP12 (D) at the 10:1 ratio of FKBP12:FKBP12.6 that is expected in situ, was able to block the subsequent addition of the other FKBP isoform (SE; n = 10–11; ^∗p < 0.05). To see this figure in color, go online.