Affiliation:
1. Department of Physiology, School of Veterinary Medicine, D-30173 Hannover, Germany
Abstract
Endogenous Pirecycling is a characteristic feature of the P homeostasis in ruminants. A pronounced salivary Pi secretion into the rumen is balanced by a high intestinal Pi absorption and an almost complete renal Pi reabsorption. In monogastric animals, the major Pi 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, Pi 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 Pi transport were characterized in goats. In the duodenum, there was an H+-dependent, Na+-sensitive Pi 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 Pi transport mainly mediated by NaPi IIb. P restriction stimulated the NaPi IIb protein expression, resulting in higher Pi transport capacity.
Publisher
American Physiological Society
Subject
Physiology (medical),Physiology
Cited by
55 articles.
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