Immunohistochemical studies on the bovine lactating mammary gland (Bos taurus).

The study aimed to evaluate the validity of immunohistochemistry in the differential labeling of the diverse components of the lactating mammary gland. Paraffin-embedded sections of lactating bovine mammary glands were stained by conventional and histochemical techniques. Primary antibodies against S100, alpha smooth muscle actin (α-SMA), connexin-43 (Cx43), cytokeratin-14 (Ck14), galactosyltransferase (GalTase), angiotensin converting enzyme (ACE) and vascular endothelial growth factor (VEGF) were applied on paraffin sections. Strong cytoplasmic and nuclear S100 immunoreactivity was mainly expressed by alveolar epithelium and to a lesser variable extent by ductal epithelium. The Golgi zone of the epithelial cells expressed strong GalTase immunostaining. Myoepithelial cells displayed a strong immunostaining for α-SMA, Cx43 and Ck14, but not for S100. Vascular endothelium showed a moderate (for VEGF) to strong (for ACE) immunostaining. The presence of VEGF-immunoreactive mast cells within the interstitium may reflect their functional significance in angiogenesis, vascular permeability and migration of mononuclear leukocytes, suggesting their regulatory role in the secretory and immunological functions of the mammary glands.