Renal reabsorption of phosphate during development: transport kinetics in BBMV.
The mechanism responsible for enhanced reabsorption of phosphate (Pi) in growing animals was assessed in renal brush-border membrane vesicles (BBMV) prepared from 3- to 14-day-old and greater than 57-day-old guinea pigs. On standard diet, Vmax (pmol.mg-1.s-1) of Na+-Pi cotransport was higher (P less than 0.001) in newborn (650 +/- 77) than in adult (144 +/- 17) but Vmax of Na+-glucose cotransport did not differ with age. Low dietary Pi did not affect significantly Vmax of Na+-Pi cotransport in the newborn (P greater than 0.8) but increased it in the adult (to 318 +/- 32, P less than 0.05). A high Pi intake resulted in a smaller relative decrease in Vmax in the newborn than in the adult (27 vs. 44%, P less than 0.05). In the newborn, the serum Pi (mM) decreased on a low-Pi diet (from 1.8 +/- 0.1 to 0.8 +/- 0.1, P less than 0.001) and rose by twofold on the high-Pi diet (to 3.5 +/- 0.2, P less than 0.001). In the adult, there were no significant changes in serum Pi with changes in Pi intake (P greater than 0.5). Thus in the newborn the Na+-Pi cotransport system is characterized by high transport capacity but low adaptability to changes in dietary Pi.
Neiberger
R E
RE
Department of Pediatrics, Albert Einstein College of Medicine, Bronx, New York 10461.
Barac-Nieto
M
M
Spitzer
A
A
D000375:Aging; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism; D004032:Diet; D005947:Glucose / Q000378:metabolism; D006168:Guinea Pigs; D007668:Kidney / Q000254:growth & development*; D007672:Kidney Cortex / Q000254:growth & development / Q000378:metabolism; D007700:Kinetics; D008871:Microvilli / Q000502:physiology*; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism*; D050608:Sodium-Phosphate Cotransporter Proteins; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D027981:Symporters
D002352:Carrier Proteins; D009004:Monosaccharide Transport Proteins; D010710:Phosphates; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters; D000469:Alkaline Phosphatase; D000254:Sodium-Potassium-Exchanging ATPase; D005947:Glucose