Direct in Vitro Effects of 1,25 (OH) 2 Vitamin D3 on Phosphate Transport in Isolated Enterocytes from Normal or Vitamin D Deficient Rats
1,25 dihydroxy vitamin D3 (1,25(OH)2 D3), the main active metabolite of vitamin D3, stimulates intestinal phosphate (Pi) absorption (1). Pi transport across the enterocyte appears to involve at least three steps (2): 1) Pi entry across the luminal brush border membrane into the enterocyte, a secondary active or facilitated process requiring energy provided by the sodium (Na+) gradient, 2) Pi transport from the mucosal to the serosal side of the cell, 3) Pi extrusion of the enterocyte into the extracellular space across the basolateral membrane. It has been proposed that 1,25(OH)2 D3 could act by altering the rate of Na+ dependent mucosal entry of Pi into the cell. However, the precise mechanism by which the hormone enhances intestinal Pi transport is still controversial.
KeywordsBrush Border Membrane Brush Border Membrane Vesicle Intestinal Brush Border Membrane Main Active Metabolite Intestinal Brush Border Membrane Vesicle
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