Staining of neuroendocrine Merkel cells of human epidermis using the uranaffin reaction.

The uranaffin reaction (UR) stains neurosecretory (NS) granules of the neuroendocrine system under certain experimental conditions of staining and rinsing solutions. Human normal neuroendocrine (NE) Merkel cells stained using the UR exhibit a positive reaction in their NS granules, ribosomes, and nuclear chromatin. The average values of maximum granular diameter (GD = 69.1 nm) and area (GA = 3637.8 mm2) of NS granules measured in the adult NE Merkel cells stained with UR are significantly greater than those (GD = 61.4 nm; GA = 2699.8 nm2) seen in the fetal NE Merkel cells also stained with UR. No differences in form factor are found between fetal and adult NS granules. On different samples of human adult and fetal epidermis it is demonstrated that UR is a useful cytochemical marker for the NS granules of normal NE Merkel cells.