Cells of Proopiomelanocortin Lineage from the Rodent Anterior Pituitary Lack Sexually Dimorphic Expression of Neurofilaments

Abstract

Lactotrophs, gonadotrophs, thyrotrophs and somatotrophs of the rat anterior pituitary (AP) express 68-kDa neurofilaments (NF68) and other neuronal markers. NF68 expression in the AP appears to be estrogen-dependent, but its significance is unknown. The aims of this work were: (1) to establish the expression pattern of NF68 immunoreactivity in the mouse AP, and (2) discover if corticotrophs and melanotrophs from both rodent species also express NF68. Primary cultures and frozen sections of AP from sexually mature mice were immunolabeled with anti-NF68 antibodies. In separate experiments, samples were immunostained for NF68 and AP hormones. Here we report that mouse lactotrophs, gonadotrophs, thyrotrophs and somatotrophs also express NF68 in a sexually dimorphic manner. The percentages of non-expressing, weakly expressing and strongly expressing cells were similar between both rodent species, although NF68+ cells were about 50% less abundant in the mouse compared to the rat pituitary. Remarkably, our study shows for the first time that rodent pituitary cells from the proopiomelanocortin lineage nearly completely lack NF68 immunoreactivity. In this regard, they differ from the rest of the AP population. Our findings establish a foundation for experiments aimed at investigating the functional significance of estrogen-dependent regulation of NF68 expression in rodent AP cells.

Immunoreactivity to Neurofilaments in the Rodent Anterior Pituitary is Associated with the Expression of α1A Protein Subunits of Voltage‐Gated Ca2+ Channels

“…1. In agreement with previous reports (2, 3), we found that the distribution of NF68 expression conforms to a Poisson distribution (Fig. 1,), with approximately 50% of the population corresponding to non‐expressing cells (i.e.…”

“…Histogram distributions of the different α1A subunits and NF68 appear in the upper and lower rows, respectively. As recently reported (3), male AP cells show little or no NF68 expression (mean ± SE = 7.12 ± 0.32), with the highest expression occurring in oestrous (mean ± SE = 56.1 ± 3.7) and intermediate expression in pro‐oestrous and dioestrous (mean ± SE = 32.2 ± 2.9 and 29.9 ± 1.7, respectively). Interestingly, α1A expression is also low in male (mean ± SE = 45.0 ± 1.7), high in oestrous and dioestrous (mean ± SE = 72.5 ± 1.5 and 69.3 ± 1.0 SE, respectively), with pro‐oestrous showing about the same expression than male (mean ± SE = 48.3 ± 1.4).…”

“…As we have previously shown, NF68 expression is sexually dimorphic (female rodents express higher levels of NF68 than males), and varies along the oestrous cycle and in response to manipulations that modify ovarian hormone concentrations or that inhibit their actions (2, 3). If, as suggested by Fig.…”

“…Expression levels of NF68 are sexually dimorphic (higher in adult females) and vary during the oestrous cycle and in response to manipulations that modify oestrogen concentrations or inhibit their actions (2, 3). These findings raised questions about the physiological significance of NF expression in AP cells and its regulation by oestrogen.…”