Phosphate transport in the duodenum and jejunum of goats and its adaptation by dietary phosphate and calcium.
Endogenous P(i) recycling is a characteristic feature of the P homeostasis in ruminants. A pronounced salivary P(i) secretion into the rumen is balanced by a high intestinal P(i) absorption and an almost complete renal P(i) reabsorption. In monogastric animals, the major P(i) transport mechanism across the apical membrane of the enterocyte is an Na(+)-dependent transport mediated by NaPi cotransporter type IIb. In ruminants, an Na(+)-, as well as an H(+)-dependent, P(i) transport system seems to exist in the small intestines. Therefore, morphological localization, type of ionic dependence, and ability to adapt to dietary P or Ca restriction of duodenal and jejunal P(i) transport were characterized in goats. In the duodenum, there was an H(+)-dependent, Na(+)-sensitive P(i) transport system that did not belong to the NaPi type II family and was not influenced by dietary P or Ca restriction. In contrast, in the jejunum, there was an Na(+)-dependent, H(+)-sensitive P(i) transport mainly mediated by NaPi IIb. P restriction stimulated the NaPi IIb protein expression, resulting in higher P(i) transport capacity.
Huber
Korinna
K
Department of Physiology, School of Veterinary Medicine, D-30173 Hannover, Germany. korinna.huber@tiho-hannover.de
Walter
Christina
C
Schröder
Bernd
B
Breves
Gerhard
G
D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002136:Calcium, Dietary / Q000378:metabolism*; D015194:Diffusion Chambers, Culture; D004386:Duodenum / Q000187:drug effects / Q000378:metabolism*; D006041:Goats; D006863:Hydrogen-Ion Concentration; D007150:Immunohistochemistry; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism; D007583:Jejunum / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D010710:Phosphates / Q000378:metabolism*; D016226:Phosphorus, Dietary / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology; D050608:Sodium-Phosphate Cotransporter Proteins; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D027981:Symporters / Q000378:metabolism
D002136:Calcium, Dietary; D010710:Phosphates; D016226:Phosphorus, Dietary; D050608:Sodium-Phosphate Cotransporter Proteins; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D027981:Symporters; D012964:Sodium