Ultracytochemical study on eccrine acrosyringium of human embryos. Acid phosphatase activity during formation of lumen.

Ultracytochemical demonstration of acid phosphatase (ACPase) activity during the developing of intraepidermal eccrine sweat duct (eccrine acrosyringium) of human embryos was performed in order to elucidate the functional relationship between multivesicular dense bodies and intracellular cavities formed within the inner cells of eccrine sweat apparatus anlagen and to clarify the ultracytochemical characteristics of the multivesicular dense bodies. ACPase activity was characteristically detected in the unit membrane structures of small pinched-off vesicles within cavities and of immature microvilli lining these cavities as well as in those of multivesicular dense bodies. These findings give strong support to the theory that the multivesicular dense bodies are lysosomes and through their action the autolytic formation of intraepidermal eccrine sweat duct is carried out.