estradiol, or let's say estrogen, has two receptors. One of them is the GRP30 (I hope I spelled it correctly) which is a G-protein coupled receptor in the cell membrane. The other is a nuclear receptor. The G-protein pathway is obviously faster, because it initiates a cascade of events by the help of adenylate cyclase (which is not a receptor), while the stimulation of nuclear receptor acts as a transcription factor which initiates transcription, then you have translation, protein modification, etc (notice how long it takes just to read it?). So basically the G-pro pathway is much faster, and I guess this is what the question means by "Primary recognition". Where did you get this question from (if I may ask)?
i thought its nuclear receptor because all steroid hormone acts by nuclear receptor...but the answer says cytoplasmic receptor if someone can explain this that will of great help.
The question is obviously outdated. Estrogen binds to its receptor in the cytoplasm, and then the hormone-receptor complex gets in nucleus to affect the transcription of several genes (it acts as a transcription factor). Recent research has shown that estrogen also has G-protein coupled receptors in the cell membrane, which react much faster than the cytoplasmic receptor (as I explained in my frist post). The correct answer in 1989 would have been cytoplasmic receptor, but now it is cell membrane receptor.
