Transport and metabolism of galactose in rat kidney cortex.
1. Analysis of transport of d-galactose was complicated by metabolism of the compound but appeared to have two components: a substrate-saturable component and a diffusion component. At low substrate concentration (<1mm) active transport was observed. Accumulation of galactose was largely independent of Na(+) concentration. The apparent K(m) for this component was 0.2mm. At substrate concentrations above 1mm the active transport system appeared saturated and further increases in substrate concentration resulted in a linear increase in the rate of galactose accumulation, but no concentration gradient was formed. 2. d-[1-(14)C]Galactose (2mm) was metabolized to (14)CO(2) by rat kidney-cortex slices incubated at 37 degrees C, at the rate of 68nmol/h per 100mg of tissue. 3. Intracellular components from such incubations were separated into a neutral fraction, the only major labelled component being galactose, and a phosphorylated fraction. 4. Phosphorylated metabolites found in galactose-incubated slices increased with increasing substrate concentration and achieved a limiting value of 0.42mm after 60min of incubation. 5. Galactose uptake was inhibited by anaerobiosis, dinitrophenol and phlorrhizin. 6. Methyl alpha-d-glucoside and d-glucose partially inhibited galactose uptake only at ratios of 100:1. 7. The presence of pyruvate did not decrease galactose metabolism although it did decrease production of (14)CO(2) from [1-(14)C]galactose. Gluconeogenesis occurred in the presence of pyruvate and (14)C from galactose was found in glucose. 8. Rat kidney-cortex slices metabolized 2mm-[1-(14)C]galactonate to (14)CO(2) at a rate of 20nmol/h per 100mg of tissue.
D000693:Anaerobiosis; D000818:Animals; D001693:Biological Transport, Active; D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes; D002848:Chromatography, DEAE-Cellulose; D002849:Chromatography, Gas; D004140:Dinitrophenols / Q000494:pharmacology; D005690:Galactose / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology; D006027:Glycosides / Q000494:pharmacology; D006601:Hexoses / Q000032:analysis; D066298:In Vitro Techniques; D007668:Kidney / Q000378:metabolism*; D007672:Kidney Cortex / Q000378:metabolism; D008297:Male; D010695:Phlorhizin / Q000494:pharmacology; D011773:Pyruvates / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000032:analysis
D002247:Carbon Isotopes; D004140:Dinitrophenols; D006027:Glycosides; D006601:Hexoses; D011773:Pyruvates; D002245:Carbon Dioxide; D012964:Sodium; D010695:Phlorhizin; D005947:Glucose; D005690:Galactose