Phosphate transport after acute changes in total NAD content in renal proximal tubules.
Suspensions of proximal tubules were obtained by collagenase digestion of rat renal cortex followed by centrifugation on a percoll gradient. NAD content in tubules incubated at 37 degrees C was decreased by 40-60% compared with tubules incubated at 4 degrees C. This change occurred within 30 min and was maintained for up to 2 hr. Inhibitors of NAD hydrolysing enzymes prevented the depletion of cellular NAD at 37 degrees C. Acute changes in proximal tubule NAD content at 37 degrees C were not accompanied by changes in phosphate uptake by brush border membrane vesicles subsequently prepared from the same tubules. In contrast, incubation of tubules with parathyroid hormone (10(-6) M) produced the expected inhibition (20%) of brush border membrane transport of phosphate. One implication of these findings is that acute changes in total NAD content of proximal tubules at 37 degrees C may not influence the phosphate transport system in the renal brush border membrane. Other interpretations are discussed.
Campbell
P I
PI
Department of Physiology, Indiana University School of Medicine, Indianapolis 46223.
Abraham
M I
MI
Dominguez
J H
JH
McAteer
J A
JA
Kempson
S A
SA
D000249:Adenosine Monophosphate / Q000032:analysis; D000255:Adenosine Triphosphate / Q000032:analysis; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002499:Centrifugation, Density Gradient; D005591:Chemical Fractionation; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D008871:Microvilli / Q000378:metabolism; D009243:NAD / Q000378:metabolism*; D010101:Oxygen Consumption; D010710:Phosphates / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013696:Temperature
D010710:Phosphates; D009243:NAD; D000249:Adenosine Monophosphate; D000255:Adenosine Triphosphate