The expression of mERα isoforms varies during the estrous cycle.

<p>Anterior pituitary cells from cycling female rats killed at diestrus I or proestrus were cultured for 24 h to allow attachment to the culture plate and then processed for cell surface biotinylation. Expression of full-length ERα (A) and its 39 kDa (B) and 22 kDa (C) isoforms was evaluated by Western blot in membrane (<i>left panels</i>) and intracellular (<i>right panels</i>) protein fractions. Densitometric data from 3–6 animals per group were normalized by the corresponding Ponceau staining (<i>left panels</i>) or β-actin value (<i>right panels</i>) and analyzed by paired Student’s <i>t</i> test, *p<0.05 vs diestrus I. Each column represents the mean ± SE of the relative increment of proestrus versus corresponding diestrus I.