Effects of fasting compared to low phosphorus diet on the kinetics of phosphate transport by renal brush-border membranes.
Changes in the kinetics of sodium gradient-dependent brush border Pi transport in response to dietary phosphorus deprivation were analysed using initial rate conditions. In rats adapted to low phosphorus diet the apparent Vmax, determined from a double-reciprocal plot, was increased 2-fold but the apparent Km was not different compared to control rats fed normal phosphorus diet. In contrast when renal adaptation to low phosphorus diet was reversed by fasting the apparent Vmax was not significantly different but the apparent Km was increased 5-fold. The results suggest that regulation of renal Pi transport in vivo may occur not only through changes in the apparent Vmax of the brush border Pi transport system but also, in certain circumstances, through changes in the apparent Km.
D000818:Animals; D001693:Biological Transport, Active; D005215:Fasting; D007672:Kidney Cortex / Q000648:ultrastructure*; D007700:Kinetics; D008871:Microvilli / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism*; D010758:Phosphorus / Q000008:administration & dosage*; D051381:Rats
D010710:Phosphates; D010758:Phosphorus