Table 3-11Chemical-specific Parameters in the Rat and Human Chromium Models

ParameteraRatHumanDefinition
Cr(IIII)Cr(VI)Cr(IIII)Cr(VI)
Absorption
  KGI0.010.040.252.5First-order rate constant for absorption from the gastrointestinal tract (Da−1)
  KLU0.22.0NANAFirst-order rate constant for absorption from the bioavailable lung pool (pool A) (Da−1)
  KMUCOA0.80.8NANAFirst-order rate constant for mucociliary clearance from pool A to the gastrointestinal tract (Da−1)
  KMUCOB0.0250.025NANAFirst-order rate constant for mucociliary clearance from the nonbioavailable lung pool (pool B) to the gastrointestinal tract (Da−1)
  KLUAB1.21.2NANAFirst-order rate constant for transfer from pool A to pool B (Da−1)
  FRLUNGNANA0.30.3Fraction of inhaled chromium absorbed to blood
  FRTRGINANA0.70.7Fraction of inhaled chromium transferred to gastrointestinal tract.
Distribution
  CR5.015.0NAbNAbRelative clearance of chromium into mineralizing bone (liters of blood plasma cleared per liter of new bone formed)
  KINRBC0.00031.512.0NAClearance from plasma to red cell (L/Da)
  KDIN0.0071.53.030.0Clearance from plasma to kidney (L/Da)
  LDIN0.00011.53.030.0Clearance from plasma to liver (L/Da)
  WDIN0.00011.53.030.0Clearance from plasma to other well-perfused tissues (L/Da)
  PDIN0.00010.013.030.0Clearance from plasma to poorly-perfused tissues (L/Da)
  BDIN0.00010.01NAbNAbClearance from plasma to bone (L/Da)
  CRNANA5.015.0Fraction deposition from blood to forming bone
  KOUTRBC0.000310.012.0NAClearance from red cell to plasma (L/Da)
  KDOUT0.00110.03.030.0Clearance from kidney to plasma (L/Da)
  LDOUT0.000310.03.030.0Clearance from liver to plasma (L/Da)
  WDOUT0.00110.03.030.0Clearance from other well-perfused tissues to plasma (L/Da)
  PDOUT0.00310.03.030.0Clearance from poorly perfused tissues to plasma (L/Da)
  BDOUT0.00310.0NAbNAbClearance from bone to plasma (L/Da)
Excretion
  KFX1.51.514.014.0First-order rate constant for loss of chromium from intestinal tract contents to the feces (Da−1)
  QEC0.0650.065NAcNAcExcretion clearance from the plasma (urinary clearance) (L/kg/Da)
  CLEARbNANA12.012.0Parameter in expression for clearance from blood plasma to urine (L/day)
  MAXbNANA0.0080.008Parameter in expression for clearance from blood plasma to urine (mg/day)
  KMbNANA0.00080.0008Parameter in expression for clearance from blood plasma to urine (mg/L)
  FB0.00.0NANAFraction of body burden secreted in the bile
  FI0.00.0NANAFraction of body burden excreted via the gastrointestinal tract
Reduction
  KREDRCNA0.7NA7.0First-order rate constant for reduction of Cr(VI) to Cr(III) in the red cell (Da−1)
  KREDBPNANANA0.2First-order rate constant for reduction of Cr(VI) to Cr(III) in blood plasma (Da−1)
  KREDKLNANANA500.0First-order rate constant for reduction of Cr(VI) to Cr(III) in kidney (Da−1)
  KREDGINA10.0NA100.0First-order rate constant for reduction of Cr(VI) to Cr(III) in gastrointestinal tract contents (Da−1)
  KREDNA0.5NA5.0First-order rate constant for reduction of Cr(VI) to Cr(III) in all other tissues and in lung contents (Da−1)
Lag time for excretion of urine
  FRHOLD0.70.7NANAFraction of urinary chromium not excreted immediately; that is, temporarily held in pool
  KHOLD0.050.05NANAFirst-order rate constant for excretion from the retained urine pool (Da−1)
  FR0.100.10NANAFraction of chromium in retained urine that is associated with the kidney
a

Parameter names are those for human model in cases where the reported rat and human parameter names were not identical.

b

Exchanges between blood plasma and cortical and trabecular bone are simulated as functions of bone formation and resorption rates.

c

QE=CLEARMAXKM+CBP , where QE is clearance from blood plasma to urine (L/day) and CBP is plasma concentration of chromium (mg/L).

NA = not applicable

Sources: O'Flaherty 1996 (rat parameters); O'Flaherty et al. 2001 (human parameters)

From: 3, HEALTH EFFECTS

Cover of Toxicological Profile for Chromium
Toxicological Profile for Chromium.
Wilbur S, Abadin H, Fay M, et al.

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