Renal inner medullary sorbitol metabolism.
Grunewald, R. W., I. I. Weber, R. K. H. Kinne.
Sektion Nephrologie, Univerist[umlaut]atsklinik Ulm, Robert-Koch
-Str. 8, D-89070 Ulm, Federal Republic of Germany, Max-Planck Institut
f[umlaut]ur Molekulare Physiologie, Rheinlanddamm 201, D-44139
Dortmund, Federal Republic of Germany
APStracts 2:0100F, 1995.
Sorbitol participates in the osmoregulation of several renal cells and
has also been found in isolated inner medullary collecting duct
(IMCD) cells in primary culture. Therefore osmotic regulation and
distribution of sorbitol, and the key enzymes of sorbitol metabolism,
aldose reductase and sorbitol dehydrogenase in the renal inner
medulla, were investigated in vivo under various osmotic conditions
(control, diuresis, antidiuresis). In homogenates of the renal inner
medulla of Wistar rats the sorbitol content correlated with the urine
osmolarity (68+/-12 U/g (control), 28+/-9 [mu]mol/g (diuresis),
110+/-15 [mu]mol/g (antidiuresis). Similar results were obtained for
the activity of aldose reductase (sorbitol synthesis) (25+/-4 U/g
(control), 19+/-3 U/g (diuresis), and 48+/-7 U/g (antidiuresis). On
the contrary the activity of sorbitol dehydrogenase (sorbitol
degradation) was significantly increased to 1.26+/-0.42 U/g under
diuretic conditions vs. control (0.84+/-0.14 U/g, p<0.05). These
results demonstrate correlation between the enzymes of sorbitol
synthesis and sorbitol degradation in the intact inner medulla and
the urine osmolarity in vivo.
Whereas the aldose reductase activity was 2.3 fold enriched in IMCD
cells, the specific activity of sorbitol dehydrogenase was relatively
increased in a preparation of enriched interstitial cells. This
distribution was not dependent on the various diuretic conditions.
These results indicate, that enzymes of synthesis and of degradation
of sorbitol are osmotically regulated in vivo. Thereby, the enzymatic
activities of sorbitol synthesis appear to be primarily located in
epithelial cells, whereas enzymatic activities of sorbitol
degradation seem to be localized in interstitial cells of the renal
inner medulla
Received 12 March 1994; accepted in final form 6 June 1995.
APS Manuscript Number F85-4.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.