Antibodies against estradiol-binding lysosomal lipoproteins gain access to the nuclear compartment of preputial gland cells under estrogen influence.

Abstract

The influence of estrogen in provoking nuclear recompartmentation of lysosomal components in hormone-sensitive cells was investigated by immunological analyses of isolated nuclei from the preputial glands of ovariectomized rats. Fixed smears were prepared from ultrapurified nuclei freed of outer membrane, 2-30 min after iv injection of placebo-control solution or submicrogram amounts of estradiol-17 beta. Cytoplasmic contamination was negligible in such preparations, as monitored by vital staining with acridine orange. On challenge with immunoglobulin G directed toward a group of lysosomal high density lipoproteins which have been shown to bind estradiol-17 beta specifically, control preparations exhibited minimal indirect immunofluorescence that was essentially confined to the nuclear periphery. In contrast, a high proportion of the nuclei exposed for as little as 2 min to estradiol-17 beta but not to the relatively inert 17 alpha-congener, displayed generally more intense immunofluorescence which was distributed over the entire organellar area. Thus, the immunoglobulin becomes accessible to the nuclear interior in vitro as a function of pretreatment in vivo with active hormone. Nuclei from estrogen-pretreated rats were more structurally labile than corresponding controls, as judged by morphological criteria, even when isolated by gentle teasing rather than subjection to the rigorous ultrapurification process. By either method, integrity of the specimens was enhanced somewhat when they were prepared from rats ovariectomized before experiencing even a single estrous cycle. The observations verify and extend independent biochemical and ultrastructural evidence that structural labilization of cellular organelles and enhanced accessibility of limited amounts of lysosomal constituents to the nuclear compartment of specific target cells are early correlates of estrogen action.