LN5-rich matrices of either 804G cells (lane 1) or MCF-10A cells (lane 2) prepared according to Langhofer et al. (1993) as well as recombinant human α3 chain G domain (lanes 3 and 4) were processed for SDS-PAGE on either 6% (lanes 1 and 2) or 7.5% (lanes 3 and 4) gels. The separated proteins were then transferred to nitrocellulose and immunoblotted with CM6 (lane 1), RG13 (lane 2 and 3), and control IgG (lane 4) antibodies. CM6 antibodies recognize rat 160-kDa α3 chain (lane 1) (Baker et al., 1996), whereas RG13 recognizes human 160-kDa α3 chain (lane 2). Whereas RG13 shows reactivity with the G domain of human α3 chain in lane 3, the control IgG does not (lane 4). Molecular mass standards of 194, 120, 87, 64, 52, 39, and 26 kDa are indicated (from top to bottom).