Ornithine decarboxylase along the mouse and rat nephron.
Levillain, Olivier, Annette Hus-Citharel.
Laboratoire de Physiopathologie M[acute]etabolique et
R[acute]enale, Facult[acute]e de M[acute]edecine Lyon R.T.H.
La[diaeresis]ennec, CRI 950201 I.N.S.E.R.M., 12, rue G. Paradin,
69372 Lyon Cedex 08, France. Laboratoire de M[acute]edecine
Exp[acute]erimentale, Coll[grave]ege de France, I.N.S.E.R.M. U 36, 3
rue d'Ulm, 75005 Paris Cedex, France
APStracts 5:0038F, 1998.
Renal arginase activity is a potent source of ornithine (Orn) for
polyamine synthesis. Ornithine decarboxylase (ODC) was localized
along the mouse and rat nephron by incubating viable nephron segments
isolated by microdissection from collagenase-treated kidneys with or
without DL-2-(difluoromethyl)ornithine (DFMO), a selective
inactivator of ODC. Tubules from either control or DFMO-treated
animals were incubated with 100 [mu]M L-[1-14C] Orn. In control mice,
Orn decarboxylation occurred mainly in the proximal convoluted tubule
(PCT). In DFMO-treated mice, Orn decarboxylation was dramatically
reduced in PCT and in proximal straight tubules (PST). In rats, Orn
decarboxylation also occurred predominantly in the proximal tubule.
Addition of 10 mM DFMO to isolated tubules dramatically decreased Orn
decarboxylation in PCT and in PST. Thereafter, ODC activity was
demonstrated in permeabilized tubules. In Triton-treated tubules from
control mice, ODC was exclusively found in proximal tubules (PCT >
PST). This ODC activity was strongly inhibited in DFMO-treated mice.
In conclusion, the highest ODC activity was found in rats and mice
PCT, a segment devoid of arginase. We hypothesize that the filtered
Orn, which is reabsorbed along the PCT, is the main source of Orn for
ODC.
Received 12 May 1997; accepted in final form 5 February 1998.
APS Manuscript Number F158-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 19 February 1998