Submitted on January 7, 2004
Accepted on February 13, 2004
Glycosaminoglycan polymerization may enable osmotically inactive Na+ storage in the skin
Jens Titze1*, Mehdi Shakibaei2, Markus Schafflhuber1, Gundula Schulze-Tanzil2, Markus Porst1, Karl H Schwind3, Peter Dietsch4, and Karl F Hilgers1
1 Department of Medicine, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
2 Department of Anatomy, Charite Berlin, Campus Benjamin Franklin, Berlin, Germany
3 Department of Chemistry and Physics, Federal Center for Meat Research, Kulmbach, Germany
4 Department of Biochemistry, Charite Berlin, Campus Benjamin Franklin, Berlin, Germany
* To whom correspondence should be addressed. E-mail: jus.titze{at}t-online.de.
Osmotically inactive skin Na+ storage is characterized by Na+ accumulation without water accumulation in the skin. Negatively charged glycosaminoglycans (GAGs) may be important in skin Na+ storage. We investigated changes in skin GAG content and key enzymes of GAG chain polymerization during osmotically inactive skin Na+ storage. Female Sprague Dawley rats were fed a 0.1% or 8% NaCl diet for 8 weeks. Skin GAG content was measured by Western blot analysis. mRNA content of key dermatan sulfate (DS) polymerization enzymes was measured by real time PCR. The Na+ concentration in skin was determined by dry ashing. Skin Na+ concentration during osmotically inactive Na+ storage was 180-190 mmol/L. Increasing skin Na+ coincided with increasing GAG content in cartilage and skin. Dietary NaCl loading coincided with increased chondroitinsynthase mRNA content in the skin, while xylosyl transferase, biglycan and decorin content were unchanged. We conclude that osmotically inactive skin Na+ storage is an active process characterized by an increased GAG content in the reservoir tissue. Inhibition or disinhibiton of GAG chain polymerization may regulate osmotically inactive Na+ storage.
