The mammary gland is an organ specific to mammals that has the task of producing and secreting milk – a vital source of nutrients for the offspring. In addition to other components, milk also consists of milk proteins, which can be divided into caseins and whey proteins. Milk protein synthesis takes place in the alveoli of the mammary gland, more precisely in the luminal cells, which are surrounded by myoepithelial cells that enable the secretion of milk components from the alveoli into the milk ducts. Our aim was to establish primary mammary epithelial cell lines from bovine milk and investigate how stimulation with lactogenic hormones affects morphology and milk protein expression. Using microscopy and immunofluorescence, we observed changes in the morphology of the cell culture and the expression of markers. Our results suggest that lactogenic hormones induce cell differentiation and influence morphology in a manner consistent with the morphology of lactating mammary glands. We confirmed the presence of myoepithelial and luminal cell subtypes. Using qPCR, we analysed the effect of lactogenic hormones on the expression of milk protein genes. Some milk protein genes are also expressed in vitro, and lactogenic stimulation can increase their expression. This increase in gene expression was also assayed at the protein level by Western bloting – however, due to the low protein concentrations in cell lysates and the growth media, we could not definitively prove the increase in protein synthesis. The results of our experiment may be useful for further research in the field of lactation biology and the effect of lactogenic hormones on mammary gland cells. Our results could also be used in livestock breeding to increase milk production and in vitro milk protein synthesis.
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