Fig. 2. Distribution of synapsin IIb protein in subcellular fractions. (A) Fractions from basal and insulin stimulated primary adipocytes; M/N, mitochondria/nuclei; PM, plasma membrane, HDM, high density microsomes; LDM, low density microsomes; cyt, cytosol. (B) Soluble (S) and particulate (P) fractions from basal L1 adipocytes (Ad) prepared by differential centrifugation (1 K=1000 g). (C) Subcellular fractions from L1 fibroblasts (Fib). Equal protein from each fraction was analyzed (10 µg for synapsin and 1 µg for Glut4) and proteins were detected using antibodies specific for Glut4 or synapsin IIb (Syn; two antibodies used, 83 and 69). In the synapsin blots using antibody 69, an additional non-specific band was detected that was also observed when the blots were probed with secondary antibody alone (2°).