title: Structural states in the Z band of skeletal muscle correlate with states of active and passive tension.
abstract: In skeletal muscle Z bands, the ends of the thin contractile filaments interdigitate in a tetragonal array of axial filaments held together by periodically cross-connecting Z filaments. Changes in these two sets of filaments are responsible for two distinct structural states observed in cross section, the small-square and basketweave forms. We have examined Z bands and A bands in relaxed, tetanized, stretched, and stretched and tetanized rat soleus muscles by electron microscopy and optical diffraction. In relaxed muscle, the A-band spacing decreases with increasing load and sarcomere length, but the Z lattice remains in the small-square form and the Z spacing changes only slightly. In tetanized muscle at sarcomere lengths up to 2.7 micron, the Z lattice assumes the basketweave form and the Z spacing is increased. The increased Z spacing is not the result of sarcomere shortening. Further, passive tension is not sufficient to cause this change in the Z lattice; active tension is necessary.
authors.affiliation: Department of Medicine, Baylor College of Medicine, Houston, Texas 77030.
authors.forename: M A
authors.initials: MA
authors.lastname: Goldstein
authors.forename: L H
authors.initials: LH
authors.lastname: Michael
authors.forename: J P
authors.initials: JP
authors.lastname: Schroeter
authors.forename: R L
authors.initials: RL
authors.lastname: Sass
mesh_terms: D000818:Animals; D008854:Microscopy, Electron; D009119:Muscle Contraction; D009132:Muscles / Q000502:physiology / Q000648:ultrastructure*; D051381:Rats; D012518:Sarcomeres / Q000648:ultrastructure