Hydrolysis of nicotinamide-adenine dinucleotide by purified renal brush-border membranes. Mechanism of NAD+ inhibition of brush-border membrane phosphate-transport activity.
Purified rat renal brush-border membrane vesicles possess a heat-labile enzyme activity which hydrolyses NAD+. A reciprocal relationship exists between the disappearance of NAD+ and the appearance of adenosine; 2 mol of Pi are liberated from each mol of NAD+ incubated with brush-border membrane vesicles. Freezing and thawing brush-border membrane vesicles does not enhance the initial rate of NAD+ hydrolysis. Preincubation of brush-border membrane vesicles with NAD+ results in inhibition of Na+-dependent Pi-transport activity, whereas Na+-dependent glucose transport is not affected. EDTA, which prevents the release of Pi from NAD+ and which itself has no direct effect on brush-border membrane Pi transport, reverses the NAD+ inhibition of Na+-dependent Pi transport. These results suggest that it is the Pi liberated from NAD+ and not NAD+ itself that inhibits Na+-dependent Pi transport.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D003864:Depression, Chemical; D004492:Edetic Acid / Q000494:pharmacology; D006868:Hydrolysis; D066298:In Vitro Techniques; D007672:Kidney Cortex / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism; D009243:NAD / Q000378:metabolism* / Q000494:pharmacology; D010710:Phosphates / Q000378:metabolism*; D051381:Rats
D010710:Phosphates; D009243:NAD; D004492:Edetic Acid