| OCR Text |
Show 75 The largest concentration of eumelanin was measured in the C57BL6 hair (37.49 ± 3.24 ug/mg). The largest concentration of pheomelanin was measured in the C57BL6 AY/a mice (29.16 ± 0.97 ug/mg). DA hair and pigmented hair from CP rats had more eumelanin than pheomelanin (up to 200-fold) despite the brown-agouti appearance of the hair. Melanin of either type was not detected in nonpigmented hair. Table 4.3 summarizes concentrations obtained from the nonselective melanin assay. Concentrations ranged from 9.97 ± 2.65 ug/mg in C57BL6 AY/a mice to 75.86 ± 10.1 in C57BL6 mice. Melanin was not detected in nonpigmented hair. Figure 4.2 shows the absorbance obtained at 500 nm vs. amount of solubilized hair from C57BL6 AY/a hair and hair from animals with predominantly eumelanin in their hair (Table 4.2). As the amount of hair increases, the absorbance at 500 nm increases for each hair type. The absorbance increase (slope) for increasing amounts of hair from the different strains ranges from 0.077x (C57BL6 AY/a) to 0.477x (C57BL6). Discussion It is possible that differences in plasma pharmacokinetics could account for differences observed in the incorporation of PCP into the hair of the rodents investigated (Table 4.2). The AUCO_8hr calculated for the rodent strains studied varied by about 2-fold (Table 4.1). The CP rats had the highest measured AUC0-8hr (37.80 ug-min/ml) but the pigmented hair concentration of PCP was only 9 ng/mg. The strain with the lowest AUCO_8hr (LE rats, 19.00 ug-min/ml) had one of the highest PCP concentrations (21.2 ng/mg) in pigmented hair. Therefore it seems unlikely that different PCP plasma pharmacokinetics contributed to differences in the amounts of PCP quantitated in the hair of the various rodent strains. The ICR normalizes the hair concentrations with respect to plasma AUCO_8hr and allows for better comparison of PCP incorporation among the various animal strains. |
