No net renal extraction of homocysteine in fasting humans.
BACKGROUND
The pathophysiological mechanism of hyperhomocysteinemia in chronic renal failure in humans is unknown. The loss of a putative renal homocysteine extraction in chronic renal failure has been hypothesized as significant homocysteine uptake has been demonstrated in the normal rat kidney. We studied homocysteine extraction in the normal human kidney.


METHODS
We measured plasma total (free and protein-bound) and free homocysteine (tHcy and fHcy, respectively) in arterial and renal venous blood sampled from the aorta and right-side renal vein during cardiac catheterization in 20 fasting patients with normal renal function. Renal homocysteine extraction was calculated as the arteriovenous difference divided by the arterial levels times 100%.


RESULTS
No significant renal extraction was demonstrated either for tHcy: 0.9% (SD 5.8; 95% CI -1.8 to +3.6) or for fHcy: -0.2% (11.0; -5.4 to +4.9).


CONCLUSIONS
We conclude that no significant net renal uptake of homocysteine occurs in fasting humans with normal renal function. The loss of such uptake, therefore, cannot cause hyperhomocysteinemia in patients with renal failure.
van Guldener
C
C
Department of Nephrology, Vrije Universiteit, Amsterdam, The Netherlands. c.vanguldener@azvu.nl
Donker
A J
AJ
Jakobs
C
C
Teerlink
T
T
de Meer
K
K
Stehouwer
C D
CD
D000368:Aged; D000596:Amino Acids / Q000097:blood / Q000652:urine; D003404:Creatinine / Q000652:urine; D005215:Fasting / Q000097:blood* / Q000652:urine*; D005260:Female; D006710:Homocysteine / Q000097:blood* / Q000652:urine*; D006801:Humans; D007668:Kidney / Q000378:metabolism; D007676:Kidney Failure, Chronic / Q000378:metabolism; D008297:Male; D008875:Middle Aged
D000596:Amino Acids; D006710:Homocysteine; D003404:Creatinine