title: Effects of seasonal changes in food quality and food intake on the transport of sodium and butyrate across ruminal epithelium of reindeer.
abstract: Transport of 22Na and 14C-butyrate across the ruminal epithelium of captive reindeer fed a concentrate diet in summer (n=5) and in winter (n=5) and from free-ranging reindeer taken from summer (n=3) and winter pasture (n=5) was measured in vitro in Ussing chambers. Significant amounts of both Na+ and butyrate were transported across the isolated epithelium without any external driving force. The ruminal transport of Na+ and butyrate were interacting, as evidenced by both the observed amiloride-induced reduction of net butyrate-transport and by the positive correlation between net transport of butyrate and Na+. Amiloride also reduced the net transport of Na+ without significantly affecting the short-circuit current, indicating the presence of an apical Na+/H+ exchanger in the ruminal epithelium of reindeer. The captive reindeer increased the dry matter intake of a constant quality concentrate from winter to summer, but this neither affected their ruminal transport capacity nor their ruminal surface enlargement factor (SEF). Free-ranging reindeer increased their ruminal transport capacity for Na+ and butyrate from summer to winter but simultaneously reduced their ruminal SEF. The present data indicate that this food-induced increase in transport capacity was attributed to changes in the nutrient composition of the diet.
authors.affiliation: Department of Arctic Biology and Institute of Medical Biology, University of Tromsø, 9037 Tromsø, Norway. paals@fagmed.uit.no
authors.forename: P V
authors.initials: PV
authors.lastname: Storeheier
authors.forename: J
authors.initials: J
authors.lastname: Sehested
authors.forename: L
authors.initials: L
authors.lastname: Diernaes
authors.forename: M A
authors.initials: MA
authors.lastname: Sundset
authors.forename: S D
authors.initials: SD
authors.lastname: Mathiesen
mesh_terms: D000584:Amiloride; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001693:Biological Transport, Active; D002087:Butyrates / Q000378:metabolism*; D002250:Carbon Radioisotopes; D004435:Eating / Q000502:physiology*; D004848:Epithelium / Q000502:physiology; D008297:Male; D009664:Norway; D012053:Reindeer / Q000378:metabolism / Q000502:physiology*; D012417:Rumen / Q000502:physiology*; D012621:Seasons; D012964:Sodium / Q000378:metabolism*; D012979:Sodium Radioisotopes
chemical_list: D002087:Butyrates; D002250:Carbon Radioisotopes; D012979:Sodium Radioisotopes; D000584:Amiloride; D012964:Sodium