Phosphate transport after acute changes in total NAD content in renal proximal tubules |
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Authors: | P I Campbell M I Abraham J H Dominguez J A McAteer S A Kempson |
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Institution: | Department of Physiology, Indiana University School of Medicine, Indianapolis 46223. |
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Abstract: | 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. |
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