ToxSci Advance Access published online on December 19, 2008
Toxicological Sciences, doi:10.1093/toxsci/kfn264
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Manganese tissue dosimetry in rats and monkeys: accounting for dietary and inhaled Mn with physiologically-based pharmacokinetic modeling
1 The Hamner Institutes for Health Sciences, 6 Davis Drive, Research Triangle Park, NC 27709 2 Afton Chemical, 500 Spring Street, Richmond, VA 23219 3 College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough Street, Raleigh, NC 27606
* Corresponding Author: Andy Nong, The Hamner Institutes for Health Sciences, 6 Davis Drive, Research Triangle Park, NC 27709-2137, anong{at}thehamner.org , (Tel) 919-558-1365 (Fax) 919-558-1300
Received August 15, 2008; revision received November 26, 2008; accepted December 10, 2008
 |
Abstract |
|---|
Nong, A., Taylor, M.D., Clewell III, H.J., Dorman, D.C., and Andersen, M.E. (2008), Manganese tissue dosimetry in rats and monkeys: accounting for dietary and inhaled Mn with physiologically-based pharmacokinetic modeling. Tox. Sci. 000, 000-000. Manganese (Mn) is an essential nutrient required for normal tissue growth and function. Following exposures to high concentrations of inhaled Mn, there is preferential accumulation of Mn in certain brain regions such as the striatum and globus pallidus. The goal of this research was to complete a physiologically-based pharmacokinetic (PBPK) model for Mn in rats and scale the model to describe Mn tissue accumulation in nonhuman primates exposed to Mn by inhalation and diet. The model structure includes saturable tissue binding with association and dissociation rate constants, asymmetric tissue permeation flux rate constants to specific tissues, and inducible biliary excretion. The rat PBPK model described tissue time-course studies for various dietary Mn intakes and accounted for inhalation studies of both 14-day and 90-day duration. In monkeys, model parameters were first calibrated using steady state tissue Mn concentration from rhesus monkeys fed a diet containing 133 ppm Mn. The model was then applied to simulate 65 exposure days of weekly (6 h/d; 5 d/wk) inhalation exposures to soluble MnSO4 at 0.03 to 1.5 mg Mn/m3. Sensitivity analysis shows that Mn tissue concentrations in the models have dose-dependencies in (1) biliary excretion of free Mn from liver, (2) saturable tissue binding in all tissues, and (3) differential influx/efflux rates for tissues that preferentially accumulate Mn. This multi-species PBPK model is consistent with the available experimental kinetic data, indicating preferential increases in some brain regions with exposures above 0.2 mg/m3 and fairly rapid return to steady state levels (within several weeks rather than months) after cessation of exposure. PBPK models that account for preferential Mn tissue accumulation from both oral and inhalation exposures will be essential to support of tissue dosimetry-based human risk assessments for Mn.
Key Words: Manganese; nonhuman primates; dose-dependent regulation; saturable tissue binding; asymmetrical diffusional flux; biliary induction; inhalation exposures; PBPK.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  M. Yoon, A. Nong, H. J. Clewell III, M. D. Taylor, D. C. Dorman, and M. E. Andersen Lactational Transfer of Manganese in Rats: Predicting Manganese Tissue Concentration in the Dam and Pups from Inhalation Exposure with a Pharmacokinetic Model Toxicol. Sci., November 1, 2009; 112(1): 23 - 43. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Yoon, A. Nong, H. J. Clewell III, M. D. Taylor, D. C. Dorman, and M. E. Andersen Evaluating Placental Transfer and Tissue Concentrations of Manganese in the Pregnant Rat and Fetuses after Inhalation Exposures with a PBPK Model Toxicol. Sci., November 1, 2009; 112(1): 44 - 58. [Abstract] [Full Text] [PDF]
|
|