Pigmented hyperplasia of epidermis following feeding of L-dopa to elderly rats.

In view of clinical data supporting a casual relationship between long-term L-dopa administration and recurrence of melanoma, long-term L-dopa administration to aged rats was performed to investigate its effect on the incidence of malignant melanoma. Of the treated animals, 11% showed local pigmented epidermal hyperplasia, compared with 0.5% of the control animals, but the number of expected melanomas was not increased by L-dopa treatment.