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Immunoreactivity to Neurofilaments in the Rodent Anterior Pituitary is Associated with the Expression of α1A Protein Subunits of Voltage‐Gated Ca 2+ Channels
Author(s) -
Fiordelisio T.,
Jiménez N.,
Baba S.,
Shiba K.,
HernándezCruz A.
Publication year - 2007
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.2007.01596.x
Subject(s) - endocrinology , medicine , neurofilament , alpha (finance) , biology , protein subunit , immunostaining , g alpha subunit , anterior pituitary , corticotropic cell , microbiology and biotechnology , hormone , immunohistochemistry , psychology , biochemistry , gene , clinical psychology , construct validity , psychometrics
We recently reported that rodent anterior pituitary (AP) cells (with the exception of corticotrophs and melanotrophs) express neuronal markers, including 68‐kDa neurofilaments (NF68) in an oestrogen‐dependent manner. The functional significance of neurofilament (NF) expression in the AP is unknown, but recent data in myelinated nerve fibres from NF‐null mice suggest that NFs can regulate ion channel function. Because Ca 2+ influx through voltage‐gated Ca 2+ channels is required for hormone secretion in AP cells, and oestrogen regulates the expression of Ca 2+ channels in AP cells, the present study examined the expression of α1 subunits of voltage gated Ca 2+ channels in relation to that of NF68. Using quantitative immunofluorescence, we demonstrate that α1C and α1D subunits are abundantly expressed in female AP cells, α1A subunits are moderately expressed, and α1G and α1B subunits are expressed at the lowest levels. Double‐immunostaining showed that NF68 expression is not correlated with that of α1C, α1D or α1B. Expression of α1G and NF68 appear to be mutually exclusive from each other. Moreover, α1A subunit and NF68 expression are significantly correlated and α1A immunoreactivity is sexually dimorphic (i.e. low in males and high in females) and its levels of expression vary during the oestrous cycle, similar to NF68. Finally, ω‐agatoxin IVA, a specific blocker of P/Q type Ca 2+ currents that are a result of the activity of α1A subunits, inhibited to a greater extent spontaneous [Ca 2+ ] i fluctuations in AP cells from females in oestrous and dioestrous, whereas cells from females in pro‐oestrous and males were less affected by this toxin. These results suggest a preferential participation of P/Q‐type Ca 2+ channels and hence α1A subunits, in regulating spontaneous Ca 2+ transients in AP cells under conditions where the proportion of NF68‐expressing cells is high. It remains to be determined whether the expression of NF68 affects that of α1A Ca 2+ channel subunits or vice versa.