[Increase of tubular secretion of creatinine by L-arginine: mechanism of practical significance in the assessment of renal function based on creatinine clearance].
BACKGROUND
Tubular secretion of creatinine is increased by meat meals. This increment has been attributed to the formation of new creatinine from creatine contained in the cooked meals. However, no studies are available using amino acid infusions containing no creatine, which allow to further investigate the putative causes of increment in tubular creatinine secretion.


METHODS
We performed a prospective, interventional study involving 34 individuals with normal renal function participating in a protocol on arterial hypertension. A continuous infusion of L-arginine (6%, i.v., in four 30 min periods at 50, 100, 200 and 300 ml/h) was administered. Creatinine (CCr) and inulin (CIn) clearances were determined at baseline and during L-arginine infusion. We analyzed the effects of L-arginine on tubular secretion by comparing CCr and CIn and calculated tubular secretion of creatinine (TSCr).


RESULTS
L-arginine infusion induced a significant increase in both CCr and CIn. CCr and CIn were respectively 117.9 +/- 22.7 and 107.5 +/- 23, before and 170.3 +/- 23 and 144.2 +/- 47.8 after the infusion of L-arginine (both p < 0.01). This increase was simultaneous with an increment in TSCr from 1.12 +/- 0.4 to 1.43 +/- 0.6 (p < 0.01). CCr correlated significantly with CIn at baseline and at 60 min of infusion (r = 0.365, p = 0.031 and r = 0.368, p = 0.038, respectively), but not at 120 min (r = 0.130, p = 0.412), a time corresponding to the maximum increase in CIn and TSCr.


CONCLUSIONS
L-arginine induces a substantial increase of CCr, which exceeds that expected from the increase in glomerular filtration rate measured by CIn and corresponds to an increment in TSCr. This phenomenon adds a new interpretation of the effect of amino acids on tubular handling of creatinine and has practical implications in the evaluation of renal function by means of creatinine clearance.
Bello
E
E
Instituto de Investigaciones Médicas, Fundación Jiménez Díaz, Universidad Autónoma, Madrid.
Caramelo
C
C
D000328:Adult; D001120:Arginine / Q000494:pharmacology*; D003404:Creatinine / Q000378:metabolism*; D006801:Humans; D007677:Kidney Function Tests; D007684:Kidney Tubules / Q000187:drug effects* / Q000378:metabolism*; D008875:Middle Aged; D011446:Prospective Studies
D001120:Arginine; D003404:Creatinine
Aumento de la secreción tubular de creatinina por L-arginina: un mecanismo con importancia práctica en la evaluación de la función renal por medio del aclaramiento de creatinina.