Figure 3. Potentiation of Ca2+-dependent force development by constituting Tn complex.
Three contractions (i, ii and iii) were successively induced by applying a bathing solution containing 1 μM [Ca2+] in chemically permeabilised strips prepared from human detrusor smooth muscle. (a) Left panel, an example trace showing a measurement of forcedevelopment; right panel, summary graph for the three successive contractions. cTnI was added to the bathing solution before the second contraction in b, and cTnC was additionally applied before the third contraction in c. The amplitude of the third contraction relative to the first one is plotted in d. The application of cTnI reduced, and the application of both cTnI and cTnC potentiated the third contraction statistically significantly (* P<0.05 and ** P<0.01, respectively, unpaired t-test). (e) Western blot examinations of Tn proteins. Lane 1 and lane 2 show before and after permeabilisation, respectively. Lane 3 and 4 correspond to the force measurement c before and after washout with relaxing solution for 30 min, respectively.