The Z-band lattice in skeletal muscle in rigor

Previous work with tetanized and relaxed muscle has shown a correlation between active tension and the structure of the Z-band. This suggests that there is a correlation between the cross-bridge binding in the A-band and the structure of the Z-band. Using electron microscopy and optical diffraction we have examined this correlation in glycerinated muscle in rigor and in unstimulated intact muscle. We have found that the Z-bands of muscles in rigor always show the basketweave form, while those of the unstimulated muscles always show the small square form. The basketweave form found in rigor muscles is similar in form and dimension to that found in tetanized muscle. Thus it appears that the small square form of the Z-band is found in physiological states with little cross-bridge binding and the basketweave form is found in states with a high degree of cross-bridge binding.