Endocrine Abstracts

Decondensation of chromatin and the pattern of its packaging in eukariotic nuclei underlie gene expression. It should be outlined that both features are determined not only by the main components of chromatin and nuclear matrix, but also by loosely bound molecules, such as phospholipids, which can interact with nucleoproteins and maintain the degree of chromatin condensation.

The steroid hormone estradiol induced changes both of total phospholipid and individual phospholipid fractions content in chromatin was examined.

Experiments were carried out on female albino mongrel rats weighting 120-150g each. Rats were sacrificed by decapitation in 4h. after hormone administration (under light ether anesthesia). Rat liver nuclei were isolated by method of Blobel & Potter, chromatin by Umansky, extraction of phospholipids by Bligh & Dyer. The quantity of each phospholipid was determined after TLC by Ames.

The in vivo action of estradiol caused reliable increase of total phospholipid content in chromatin. The hormone increased the amount of four from six phospholipid fractions when acting in concentration and exposition time that cause activation of biosynthetic processes. At the same time content of major phospholipid fraction of this subnuclear structure - phosphatidylcholine was decreased which indicates the redistribution between phospholipid fractions of chromatin under the steroid hormone action. Elevation of sphingomyelin and phosphatidylinositol is of special interest from the viewpoint of downstream pathways of signal transducting systems. Taking for account the functioning of sphingomyelin and phosphoinositide signaling mechanisms in nuclei we aim to reveal possible cross talking of both signaling systems as a field where steroid hormone induced genomic and non-genomic effects may be pronounced.