AJP - Renal Physiology, Vol 271, Issue 6 1255-F1263, Copyright © 1996 by American Physiological Society
NaCl and/or urea infusion fails to increase renal inner medullary myo-inositol in protein-deprived rats
T. Nakanishi, F. Nishihara, A. Yamauchi, S. Yamamoto, M. Sugita and Y. Takamitsu
Department of Kidney and Dialysis, Hyogo College of Medicine, Nishinomiya, Japan.
As we recently demonstrated that in potassium depletion a decrease in inner
medullary organic osmolytes might precede and cause a renal concentrating
defect, we hypothesized that in the protein deprivation the same mechanism
may occur. To clarify the relationship between renal medullary organic
osmolytes and urine concentration defects during protein deprivation, we
examined the effect of protein malnutrition on organic osmolyte content
after water deprivation or sodium and/or urea infusion. Water deprivation
did not restore urine urea and osmolality or tissue sodium and urea in
protein-deprived rats to control levels. NaCl infusion only increased
urinary and medullary Na. Urea infusion increased medullary urea but not
urine urea. NaCl plus urea infusion increased only urinary sodium and urea.
Regardless of the protocols of hyperosmolality used, protein deprivation
significantly decreased the medullary contents of myo-inositol and taurine
and the level of sodium-dependent myo-inositol transporter mRNA. We
conclude that factors other than NaCl and urea but associated with protein
feeding are responsible for the decreased accumulation of organic
osmolytes.
