Submitted on May 6, 2005
Accepted on June 30, 2005
Human Sulfate Kinetics
L. John Hoffer1*, Mazen J Hamadeh1, Line Robitaille1, and Kenneth H Norwich2
1 Lady Davis Institute for Medical Research-Jewish General Hospital, McGill University, Montreal, Quebec, Canada
2 Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
* To whom correspondence should be addressed. E-mail: l.hoffer{at}mcgill.ca.
Electrospray tandem mass spectrometry was used to determine steady state serum and urinary inorganic sulfate and sulfate ester kinetic profiles of 9 normal men following intravenous injection of the stable isotope sodium [34S]sulfate. Sulfate ester appearance was traced by eliminating inorganic sulfate from samples, followed by hydrolysis of sulfate esters to inorganic sulfate for analysis. Whole-body inorganic sulfate turnover in steady state was calculated by standard tracer techniques. Rate of appearance and disappearance of inorganic sulfate was 841 ± 49 µmol/h. Average urinary inorganic sulfate excretion was 609 ± 41 µmol/h and the whole-body sulfation rate (total rate of disappearance minus rate of urinary excretion) was 232 ± 36 µmol/h. Tracer-labeled sulfate esters appeared in serum and urine within 1 h of tracer injection. The kinetics of inorganic sulfate and sulfate esters were linked by means of a compartmental model. The appearance and excretion of sulfate esters accounted for ~ 50% of the total sulfation rate. These results indicate that human whole-body sulfation accounts for ~ 27% of inorganic sulfate turnover, and that extracellular inorganic sulfate is an important pool for intracellular sulfation. A substantial fraction of newly synthesized sulfate esters promptly enters the extracellular space for excretion in the urine.
