Metabolism of cyclic adp-ribose in opossum kidney renal epithelial
cells.
Beers, Kelly W., Eduardo N. Chini, Hon Cheung Lee, and Thomas P. Dousa.
Nephrology Research Unit, Division of Nephrology and Department of
Physiology,
Mayo Clinic and Foundation, Rochester, MN 55905; and Department of
Physiology, University of Minnesota, Minneapolis, MN 55455
APStracts 2:0001C, 1995.
We have previously shown that NAD+ inhibits renal Na+-Pi symport, however the
biochemical mechanism of NAD+ in this action is not clarified. We now propose
that NAD+ acts indirectly, by first being converted to cyclic ADP-ribose
(cADPR), a potent stimulator of intracellular calcium mobilization. In
permeabilized opossum kidney (OK) cells, a cell line often employed as a
model for study of proximal tubular epithelial transport, cADPR is
synthesized from [beta]-NAD+ in a substrate-concentration (0.01-1 mM) and time
-dependent manner. That cADPR was generated from [beta]-NAD+ by OK cells was
verified by co-elution with authentic cADPR on anion exchange HPLC and by
homologous desensitization of the Ca2+ release bioassay to authentic cADPR.
cADPR synthesized by permeabilized OK cells was not influenced by the
addition of parathyroid hormone. The OK cell also contains the enzyme
activity necessary to catalyze catabolism of cADPR. Identification of these
two key enzyme activities of cADPR metabolism in OK cells is consistent with
a possible role of cADPR in regulation of the Na+-Pi symporter by NAD+ in
response to metabolic stimuli.
ed 4 August 1994; accepted in final form 14 October 1994
APS Manuscript Number C461-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1994 The American Physiological Society.
Published in APStracts on 27 February 1995.