Fig. 1. An increase in IGFBP-5 expression occurs concomitantly with DNA fragmentation during mammary gland involution. (A) Whole tissue lysates from different stages of development were analysed by 15% SDS-PAGE and ligand blotting with I¹²⁵-IGF-I. Tissue was taken from virgin animals (V); mice pregnant for 9 and 15 days after detecting a vaginal plug (P9 and P15); mice in full lactation for 9 days (L9); and mice where the pups had been removed for up to 5 days following a 9-day lactation period (I1-5). Samples of recombinant IGFBP-1, -3 and -5 were included as reference markers and the E-cadherin levels of the samples were analysed by immunoblotting (IB) to confirm equal epithelial cell content. (B) Lysates from duplicate samples were immunoprecipitated (IP) with an antibody against IGFBP-5 prior to I¹²⁵-IGF-I ligand blotting. (C) DNA extracted from mammary gland tissue from different stages of development was separated on a 1.2% agarose gel and was stained with ethidium bromide. Results are representative of three sets of tissue.