In:
American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, American Physiological Society, Vol. 303, No. 9 ( 2012-11-01), p. R909-R920
Kurzfassung:
Ruminal vacuolar H + -ATPase (vH + -ATPase) activity is regulated by metabolic signals. Thus, we tested whether its localization, expression, and activity were changed by different feeding. Young male sheep ( n = 12) were either fed hay ad libitum (h) or hay ad libitum plus additional concentrate (h/c) for 2 wk. The vH + -ATPase B subunit signal was predominantly found in the cell membrane and cytosol of rumen epithelial cells (REC) with basal/parabasal phenotype. The elevated number (threefold) of these cells in rumen mucosa of h/c-fed sheep reflects a high proliferative capacity and, explains the 2.3-fold increase of the total number of vH + -ATPase-expressing REC. However, in accordance with a 58% reduction of the vH + -ATPase B subunit mRNA expression in h/c-fed sheep, its protein amount per single REC was decreased. Using the fluorescent probe BCECF and selective inhibitors (foliomycin, amiloride), the contribution of vH + -ATPase and Na + /H + exchanger to intracellular pH (pH i ) regulation was investigated. REC isolated from h/c-fed sheep keep their pH i at a significantly higher level (6.91 ± 0.03 vs. 6.74 ± 0.05 in h-fed sheep). Foliomycin or amiloride decreased pH i by 0.16 ± 0.02 and 0.57 ± 0.04 pH units when applied to REC from h-fed sheep, but the effects were markedly reduced (−88 and −33%) after concentrate feeding. Nevertheless, we found that REC proliferation rate and [cAMP] i were reduced after foliomycin-induced vH + -ATPase inhibition. Our results provide the first evidence for a role of vH + -ATPase in regulation of REC proliferation, most probably by linking metabolically induced pH i changes to signaling pathways regulating this process.
Materialart:
Online-Ressource
ISSN:
0363-6119
,
1522-1490
DOI:
10.1152/ajpregu.00597.2011
Sprache:
Englisch
Verlag:
American Physiological Society
Publikationsdatum:
2012
ZDB Id:
1477297-8
SSG:
12
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