A COMPARISON OF H-3 COCAINE BINDING ON MELANIN GRANULES AND HUMAN HAIR IN-VITRO

The in vitro experiments on the interaction of H-3-cocaine and melanin from Sepia officinalis confirmed the existence of drug binding sites on melanin granules. The results suggested that the binding of H-3-coc aine to melanin could be analyzed by assuming that the binding to the surface of pigment granules is analogous to the adsorption of a drug o n a solid and follows Langmuir adsorption isotherm type I. Scatchard a nalysis indicated heterogeneity of binding sites. Structural and chemi cal alterations caused by isolation of the melanoproteins, which are h eterogenous in nature and show different physicochemical properties, a re considered to be most crucial. The studies on hair samples confirme d that melanin-drug interactions occur on the surface of melanin granu les. These seem to be of minor importance compared to the drug-melanop rotein loading during melanogenesis for the observed influence of pigm entation on the drug content of hair fibers. From the results it was c oncluded that in vitro studies on melanin provide limited information and even drug-soaked hair must be regarded as inappropriate for the st udy of melanin-drug-binding in hair.