{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,15]],"date-time":"2026-08-15T10:48:55Z","timestamp":1786790935819,"version":"build-2736575974"},"reference-count":44,"publisher":"American Physiological Society","issue":"5","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["American Journal of Physiology-Cell Physiology"],"published-print":{"date-parts":[[2007,5]]},"abstract":"<jats:p> Mammary epithelia produce an isotonic, low-Na<jats:sup>+<\/jats:sup> fluid that is rich in nutrients. Mechanisms that account for the low electrolyte concentration have not been elucidated, although amiloride-sensitive ion transport has been reported in some situations. We hypothesized that corticosteroid exposure modulates epithelial Na<jats:sup>+<\/jats:sup> channel (ENaC) expression and\/or activity in bovine mammary epithelial cells. BME-UV cells were grown to confluent monolayers on permeable supports with a standard basolateral medium and apical medium of low-electrolyte, high-lactose composition that resembles the ionic composition of milk. Ion transport was assessed in modified Ussing flux chambers. Exposure to glucocorticoids (dexamethasone, cortisol, or prednisolone), but not aldosterone, increased short-circuit current ( I<jats:sub>sc<\/jats:sub>), a sensitive measure of net ion transport, whereas apical exposure to amiloride or benzamil reduced corticosteroid-induced I<jats:sub>sc<\/jats:sub> close to basal levels. Quantitative RT-PCR indicated a glucocorticoid-induced increase in mRNA for \u03b2- and \u03b3-ENaC, whereas \u03b1-ENaC mRNA expression was only mildly affected. Exposure to mifepristone (a glucocorticoid receptor antagonist), but not spironolactone (a mineralocorticoid receptor antagonist), precluded both the corticosteroid-induced elevation in amiloride-sensitive I<jats:sub>sc<\/jats:sub> and the induced changes in \u03b2- and \u03b3-ENaC mRNA. We conclude that Na<jats:sup>+<\/jats:sup> movement across mammary epithelia is modulated by corticosteroids via a glucocorticoid receptor-mediated mechanism that regulates the expression of the \u03b2- and \u03b3-subunits of ENaC. ENaC expression and activity could account for the low Na<jats:sup>+<\/jats:sup> concentration that is typical of milk. <\/jats:p>","DOI":"10.1152\/ajpcell.00369.2006","type":"journal-article","created":{"date-parts":[[2007,1,25]],"date-time":"2007-01-25T05:49:31Z","timestamp":1169704171000},"page":"C1739-C1745","source":"Crossref","is-referenced-by-count":20,"title":["Glucocorticoids stimulate ENaC upregulation in bovine mammary epithelium"],"prefix":"10.1152","volume":"292","author":[{"given":"Rebecca R.","family":"Quesnell","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xiaobin","family":"Han","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bruce D.","family":"Schultz","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"24","reference":[{"key":"R1","doi-asserted-by":"crossref","unstructured":"Berger HA, Welsh MJ. 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