Estrous-cycle-dependent hippocampal levels of signaling proteins.

There is information that proteins are expressed in a hormone-dependent manner but no systematic study on this subject has been carried out to the best of our knowledge. We therefore decided to investigate protein expression in a well-studied brain area, the hippocampus, in female rats at various phases of the estrous cycle and in male rats. Male and female OFA Sprague-Dawley rats were used in the studies and estrous phases were determined using vaginal smears and females were grouped according to PE, E, ME, and DE. Hippocampal tissue was taken, proteins extracted, run on two-dimensional gel electrophoresis and proteins were identified by mass spectrometry methods (MALDI-TOF-TOF and nano-LC-ESI-MS/MS). Individual signaling protein levels quantified by specific software were shown to depend on sex and phase of the estrous cycle. These include NG,NG-dimethylarginine dimethylaminohydrolase for nitric oxide signaling, stathmin, SH3 domain protein 2A, SH3 domain protein 2B, S100 calcium binding protein B, calcyclin-binding protein, Syndapin I, GTPase HRas, guanine nucleotide-binding proteins, septin 8, G-septin alpha, phosphtidylethanolamine-binding protein, several protein phosphatases. Results from this study, although increasing complexity of protein knowledge, may help to design further investigations at the protein level and may assist to interpret literature on protein expression and brain protein levels.