Differentiation of subgroups of type 2B with Sudan black B staining in rat skeletal muscle

Using tibialis anterior, gastrocnemius lateralis, and masseter muscles of a male and a female normal Wistar rat, we examined the sensitivity of SBB staining to these muscles. We recognized that type 2A, 2B, and other types (type I, 2C and 2X) were darkly, lightly, and moderately stained by the SBB staining. Type 2B fibers identified by mATPase could be divided clearly into two subgroups by SBB staining. The dark population was type 2Bd that corresponded to type 2X, and the moderate one was 2Bm. Therefore, through the SBB staining it was possible to identify type 2Bd (2X) and 2Bm, as it is with SDH staining.