The Z band in skinned fibers of a slow skeletal muscle

We have shown that Z bands in rat soleus muscles exhibit two structural states. The small square (ss) form is seen in relaxed intact muscle and the basketweave (bw) form is seen in maximally activated muscle (tetanized and in rigor). The Z spacing measured in the bw form is 20% larger than that in the ss form. The dimensions of the two Z band lattice forms in these muscle states are independent of A band spacing. Skinned fibers have been used to assess various muscle properties and expansion of the A band has been observed in some cases. We have examined the effects of chemical skinning on Z band form and dimension and A band spacing in relaxed muscle. Rat soleus muscles were dissected and tied to applicator sticks and removed to a solution of 1% Triton X-100 in lOmM PIPES buffer with 5mM EGTA and lOmM ATP overnight at 4°C, then rinsed with the PIPES buffer with EGTA and ATP only for 4 hours.