| OCR Text |
Show 79 playa role in the selective incorporation of PCP into pigmented hair verses nonpigmented hair. One possible mechanism is an ionic interaction between PCP and eumelanin, as suggested in Chapter 3. It can be speculated that the selective incorporation of other drugs such as codeine, cocaine, methadone and nicotine into pigmented hair is due to an interaction with melanin, specifically eumelanin in hair. In nonpigmented hair, PCP was detected, but melanin was not present. This suggests that melanin is not the only factor affecting the incorporation of PCP in hair. Codeine, morphine, cocaine and phenobarbital have been quantitated in nonpigmented hair which suggests that factors other than melanin are involved in the incorporation and retention of these drugs in nonpigmented hair (60-62, 65, 69, 134). These factors probably involve keratins in hair, but no reports are available that link the incorporation of drugs into hair to specific interactions with keratins (see Chapter 1). An area of concern in the interpretation of the melanin data presented here was the comparison of the results obtained in the selective assay for ph eo melanin with the total melanin assay for the yellow-haired (C57BL6 AY/a ) mice. Pheomelanin (29 ug/mg) was measured in C57BL6 AY/a hair from the selective HPLC assay, whereas, only 9 ug/mg of total melanin was calculated in the same hair using the nonselective (total) melanin assay (Table 4.2 and 4.3). One of the specific concerns with quantitating total melanin in pheomelanin-containing tissues using the nonselective melanin assay is the fact that sepia melanin is used as the quantitative standard. It has been previously shown that sepia melanin is predominantly eumelanin (112). If pheomelanin has different absorbance characteristics at 500 nm compared to eumelanin, the quantitative accuracy of the melanin measurements would be compromised when eumelanin (sepia) is used as the quantitative standard to evaluate pheomelanin-containing tissue (i.e., C57BL6 AY/a). To investigate this further, increasing amounts of C57BL6 AY/a mouse hair were subjected to the total melanin assay and the absorbance at 500 nm were determined. This same procedure was performed with hair determined to contain predominantly eumelanin, according to the |
