Distribution of de novo synthesized betaine in rat kidney: role of
renal betaine synthesis on medullary betaine accumulation.
Moeckel, Gilbert W., and Yeong-Hau H. Lien.
Department of Medicine, Section of Renal Disease, University of
Arizona Health Sciences Center, Tucson, Arizona 85724
APStracts 3:0179F, 1996.
The trimethylamine glycine-betaine is accumulated to high
concentrations in medullary cells of mammalian kidneys, while betaine
synthesis from choline is predominant in the renal cortex. We
investigated the contribution of renal betaine synthesis to medullary
betaine accumulation. De novo synthesis of betaine in situ was
accomplished by injecting [14C]choline into the renal artery of male
Sprague-Dawley rats. [14C]betaine was measured in the renal cortex
and medulla, as well as in serum and urine samples. Betaine
concentration in the cortex decreased from 3.5+/-1.3 nmol/mg protein
at 5 min to 0.4+/-0.2 at 60 min, but it increased from 1.4+/-0.1
nmol/mg protein to 2.5+/-0.6 in the medulla. Serum and total urine
[14C] betaine increased from 2.7+/-1.3 nmol/ml and 0.9+/-0.1 nmol at
5 min to 5.3+/-0.3 and 2.1+/-0.4 at 60 min, respectively.
Concentrations of newly synthesized betaine were not decreased by the
ligation of the hepatic artery and portal vein suggesting that most
[14C]betaine was synthesized in the kidney. Co-injection with 5 mM
dimethylaminoethanol, a choline oxidase inhibitor, and 100 mM cold
betaine reduced medullary betaine accumulation by 80% and 76%,
respectively. Water deprivation for 60 h increased both cortical and
medullary [14C]betaine, while furosemide diuresis decreased the
medullary [14C]betaine concentration. We concluded that betaine
synthesized in the kidney can be accumulated in the medulla and that
the medullary concentrations of newly synthesized betaine are closely
related to the hydration state of the animal.
Received 21 May 1996; accepted in final form 20 September 1996.
APS Manuscript Number F157-6.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996