Influence of tamoxifen treatment on mammary stromal fibroblasts and macrophages. (a) Motility of primary mammary fibroblasts isolated from individual control rats (Ctl; n = 7), tamoxifen-treated rats (Tam; n = 10), and pooled populations (insert). (b) One-dimensional gel of extracellular matrix (ECM) proteins laid down in culture by primary mammary fibroblasts isolated from control and tamoxifen-treated rats. Arrow shows about a prominent 250 kD band identified as containing fibronectin (FN) by mass spectrometry, which is present in control ECM and greatly reduced in tamoxifen ECM. Lane 3 depicts molecular weight (MW) marker. (c) upper panel: 5 μm representative sections of mammary glands stained for CD68, a macrophage lysosomal-associated protein. 400× magnification. (c) lower panel: Quantitation of CD68 positive mammary cells in control (n = 6) and tamoxifen-treated (n = 6) rats demonstrates significantly fewer macrophages with tamoxifen treatment (*p = 0.013).