Immunomicroscopy of neurofilaments in chromaffin cells of the adult bovine adrenal gland

Abstract

Neurofilaments (NFs) represent a class of intermediate filaments which are highly specific for neurons. The most abundant of the native NFs is the 68 kD subunit (NF-L). Chromaffin cells of the adrenal medulla express NF subunits under culture conditions. However, NF expression in situ is questionable. It has been reported that as chromaffin cell precursors mature and begin to express catecholamine-synthesizing enzymes, their neuronal traits are extinguished and they become endocrine-like cells. This study reports that while NF-L may be lacking in the adrenal medulla of some species, NF-L immunoreactivity is clearly present in the adult bovine adrenal medulla. Immunofluorescence microscopy of bovine chromaffin cells in culture demonstrated NF immunoreactivity localized to both thin, highly ramified filaments present throughout the cell and frequently to an intensely immunofluorescent spot located near the nucleus. Double-label immunofluorescence microscopy and immunoblot analysis also demonstrated NF-L immunoreactivity in mature chromaffin cells of the bovine adrenal gland. In vitro and in situ immunofluorescence results were confirmed by immunogold and immunoperoxidase labelling, respectively. In both cases, NF-L immunoreactivity was associated with filaments in close proximity to the nucleus. Additionally, a spheroidal aggregate of immunogold-labelled NFs was seen adjacent to the nucleus in cultured cells. In conclusion, NF-L in bovine chromaffin cells demonstrates that at least one neuronal trait persists in these catecholamine-producing cells of the mature adrenal gland. In addition, this study emphasizes the fact that interspecies comparisons must be interpreted with caution, especially when attempting to formulate a generalized hypothesis.

Oestrogen Regulates Neurofilament Expression in a Subset of Anterior Pituitary Cells of the Adult Female Rat

“…Even when previous studies demonstrated that pituitary cells in culture can maintain their functional differentiation for several weeks, and sometimes for months (17), it could be argued that the synthesis of neuronal markers could reflect an anomalous condition resulting from tissue dissociation or culture conditions. In this regard, it should be mentioned that adrenal chromaffin cells, which do not express NFs in situ , can express them under culture conditions (18). To rule out this possibility, NF68 immunolabelling was conducted in 5 µm‐thick sections of intact pituitary glands.…”

Nestin expression in rat adrenal gland

“…With the exception of adult bovine adrenal medulla that has been reported to express NF-L immunoreactivity (Yang et al 1996), based on the data currently available chromaffin cells seem devoid of a network of known IFs, not displaying detectable levels of vimentin, neurofilaments or cytokeratins (Ehrlich et al 1994;Kameda 1996;Quintanar 2000). For this reason the demonstration of in situ expression of nestin within adult rat adrenomedullary cells appears of particular interest.…”