![Sample our Bioscience journals, sign in here to start your access, Latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5925/TOC-Subject-Sample-2021-Bioscience.jpg"})
Abstract
Autocrine production of growth factors can have significant effects on cell activity. We report for the first time that autocrine production of insulin-like growth factor–I (IGF-I) alters paracellular transport across bovine mammary epithelial cells in vitro. Paracellular transport was assessed by measuring phenol red transport across mammary alveolar cells–large T antigen (MAC-T cells) derived from parental mammary epithelial cells, cultured on porous membranes and compared with two different transfected MAC-T cell lines that constitutively secrete IGF-I. Phenol red transport was essentially blocked in parental cell culture after six days, while IGF-I secreting cells provided essentially no barrier. Surprisingly, neither co-culture studies between parental and IGF-I–secreting cells nor addition of exogenous IGF-I or IGF-binding protein–3 reversed the phenol red transport properties. IGF-I–secreting cells did however express lower levels of the junction components occludin and E-cadherin than parental cells, suggesting that localized autocrine IGF-I activity might lead to increased permeability via changes in both the tight and adherens junction protein levels.