NACL AND OR UREA INFUSION FAILS TO INCREASE RENAL INNER MEDULLARY MYOINOSITOL IN PROTEIN-DEPRIVED RATS/

As we recently demonstrated that in potassium depletion a decrease in inner medullary organic osmolytes might precede and cause a renal conc entrating defect, we hypothesized that in the protein deprivation the same mechanism may occur. To clarify the relationship between renal me dullary organic osmolytes and urine concentration defects during prote in deprivation, we examined the effect of protein malnutrition on orga nic osmolyte content after water deprivation or sodium and/or urea inf usion. Water deprivation did not restore urine urea and osmolality or tissue sodium and urea in protein-deprived rats to control levels. NaC l infusion only increased urinary and medullary Na. Urea infusion incr eased medullary urea but not urine urea. NaCl plus urea infusion incre ased only urinary sodium and urea. Regardless of the protocols of hype rosmolality used, protein deprivation significantly decreased the medu llary contents of myo-inositol and taurine and the level of sodium-dep endent myo-inositol transporter mRNA. We conclude that factors other t han NaCl and urea but associated with protein feeding are responsible for the decreased accumulation of organic osmolytes.