Manometric and Histochemical Demonstration of Tyrosinase in Foetal Guinea-pig Skin

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Abstract
Procedures are descr. for demonstrating tyrosinase activity, both manometrically and histochemicaliy, in the same sample of normal pigmented fetal guinea-pig skin. These procedures involve the use of skin ground while frozen and then suspended in distilled water. A Warburg respirometer is used to determine O2 consumption related to the enzymatic oxidation of tyrosine. After the Warburg run, skin fragments incubated in the presence (exptls.) and absence (controls) of tyrosine are removed from the reaction vessels and are then compared histologically. Exptl. skin fragments show much more hair bulb pigmentation than the controls. These results help establish the role of tyrosine as a melanin precursor in normal mammalian skin. In the case of the guinea-pig, however, there is no simple parallelism between demonstrable tyrosinase or dopa oxidase activity and genetically detd. amt. or kind of natural pigment.