ELEVATED PLASMA-CORTISOL REDUCES PERMEABILITY OF MAMMARY TIGHT JUNCTIONS IN THE LACTATING BOVINE MAMMARY EPITHELIUM

Citation
K. Stelwagen et al., ELEVATED PLASMA-CORTISOL REDUCES PERMEABILITY OF MAMMARY TIGHT JUNCTIONS IN THE LACTATING BOVINE MAMMARY EPITHELIUM, Journal of Endocrinology, 159(1), 1998, pp. 173-178
Citations number
36
Categorie Soggetti
Endocrynology & Metabolism
Journal title
ISSN journal
00220795
Volume
159
Issue
1
Year of publication
1998
Pages
173 - 178
Database
ISI
SICI code
0022-0795(1998)159:1<173:EPRPOM>2.0.ZU;2-5
Abstract
Induction of tight junction permeability in the mammary epithelium dec reases milk secretion, and in cows tight junctions become leaky after 17 h of milk accumulation. In vitro studies demonstrate the importance of glucocorticoids for the formation and maintenance of tight tight j unctions. In this study we examined whether cortisol can prevent mamma ry tight junction permeability in the lactating gland in vivo, and inh ibit the associated milk loss, using our milk-accumulation model to ch allenge tight junction patency. Following a 4-day control period Jerse y cows were subjected to a 24-h period in which they were milked twice at 0700 and 1500 h (TM; n=6), once at 0700 h (OM; n=7), or once and t reated with ACTH (40 IU per 2 h, starting after 14 h of milk accumulat ion) to increase endogenous cortisol levels (OM+ACTH; n=7). Frequent b lood samples for cortisol, lactose and glucose analyses were taken via indwelling jugular catheters. ACTH treatment resulted in a sustained elevation of systemic cortisol concentrations. Plasma lactose, an indi cator of tight junction leakiness, was not changed in TM cows, but beg an to increase rapidly at 17 h oi milk accumulation in OM cows. Treatm ent with ACTH prevented the increase in plasma lactose, although level s were slightly, but not significantly, higher than in TM cows, indica ting that elevated plasma cortisol reduced mammary tight junction leak iness. Milk yield was reduced by 12% in both once-milked groups, despi te cortisol preventing tight junction leakiness. However, the milk los s in the latter group may not be related to leaky tight junctions, but be due to a reduction in milk precursor uptake by the mammary gland. Consistent with this notion was a 34% increase in plasma glucose level s in OM+ACTH cows only.