Intestinal maturation: characterization of mitochondrial phosphate transport in the rat and its regulation by 1,25-(OH)2 vitamin D3.
The mitochondria play a major role in the regulation of oxidative phosphorylation within the cell. Despite the fact that the enterocytes receive the majority of absorbed phosphate and their high metabolic turnover rate, the role of the intestinal mitochondria in phosphate transport system during maturation is not known. Therefore, the current studies were designed to characterize phosphate transport by jejunal mitochondria of rats during maturation (suckling, weanling, and adolescent rats). The functional integrity of the intestinal mitochondria of suckling and adolescent rats was determined by oxygen consumption studies demonstrating respiratory control ratios of more than 3 when succinate was used as a test substrate. Phosphate uptake was significantly stimulated by the presence of 3 mM ATP at all age groups studied. Maximal phosphate uptake in the presence of 3 mM ATP and 2 mM succinate was 16.5 +/- 1.0, 20.5 +/- 1 and 28.7 +/- 0.4 nmol/mg protein (mean +/- SE) in suckling, weanling, and adolescent rats respectively. ATP-dependent phosphate uptake was inhibited by 80% with 100 microM p-MB. Kinetic parameters for ATP stimulated phosphate uptake at 10 s revealed a Km of 4 +/- 0.9, 2.8 +/- 0.4, and 0.9 +/- 0.1 mM and Vmax of 5 +/- 0.7, 9.5 +/- 1, and 11 +/- 0.7 nmol/mg protein per 10 s in suckling, weanling, and adolescent rats, respectively. Phosphate uptake was also stimulated by an inwardly directed pH gradient (pH out less than pH inside) compared to no pH gradient condition suggesting the presence of PO4-/OH- exchange.(ABSTRACT TRUNCATED AT 250 WORDS)
Kikuchi
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T
Vanderbilt University School of Medicine, Department of Pediatrics, Nashville, Tennessee 37232.
Arab
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NL
Kikuchi
K
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Ghishan
F K
FK
D000255:Adenosine Triphosphate / Q000502:physiology; D000375:Aging / Q000378:metabolism*; D000818:Animals; D000833:Animals, Suckling; D002117:Calcitriol / Q000502:physiology*; D007583:Jejunum / Q000254:growth & development*; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D010710:Phosphates / Q000493:pharmacokinetics*; D051381:Rats; D011919:Rats, Inbred Strains; D014886:Weaning
D010710:Phosphates; D000255:Adenosine Triphosphate; D002117:Calcitriol