Ultrastructure and neuron-specific enolase (NSE) immunohistochemistry of Merkel cells in normal toad epidermis, and following ablation of the pars distalis of the pituitary gland.

The present study was performed in order to re-examine the possible Merkel cell dependency upon the anterior pituitary by a combined ultrastructural and NSE immunohistochemical analysis of Merkel cells in normal toads, and following pars distalis ablation. Ultrastructurally, toad Merkel cells appeared similar to those in previous reports. They were found in normal as well as in operated toads, but with lower frequency in the latter group. By NSE immunohistochemistry, Merkel cells were seen in normal toads only. Even in individual, operated toads, in which Merkel cells were found with relative high frequency by electron microscopy, no NSE could be demonstrated immunohistochemically. It is discussed whether the amount of NSE present depends upon the physiological state of the Merkel cell and in some cells occurs in so low an amount that the NSE antigen cannot be detected by the immunocytochemical method applied. If it is so, the failure to demonstrate Merkel cells in the operated toads by means of the specific marker NSE may be interpreted as an inhibition of NSE expression following pars distalis ablation. This interpretation combined with the lower number of Merkel cells found ultrastructurally in operated toads support a previous indication of an influence of the anterior pituitary--directly or indirectly--upon toad Merkel cell function.