Melanin containing organelles in cells of the human gingiva. II. Keratinocytes.

Abstract

Biopsies of the marginal gingiva obtained from 21 caucasoid subjects (average age of 25 years) served for the electron microscopic examination of melanin containing organelles in keratinocytes of the oral epithelium. Basal and suprabasal keratinocytes situated at epithelial rete pegs of the free and attached gingiva were observed to contain granules of melanin representing premelanosomes as well as single and compound melanosomes. These organelles were either randomly distributed or preferentially located at the cell poles or arranged around the nucleus. Single melanosomes were 0.31 ± 0.08 micron long and 0.12 ± 0.04 micron wide. Compound melanosomes were areas, 0.36 ± 0.12 micron in diameter, bound by a unit membrane and containing numerous single melanosomes which in part appeared to dissolve in granules. There was a centrifugal transport of melanin containing organelles with advancing keratinocytes. Single and compound melanosomes were occasionally found in cells up to the upper stratum spinosum. The findings are discussed with regard to comparable observations as well as in connection with the prevailing theories of melanin transfer and degradation.