The interactions and mechanisms by which estrogen induces Type IV hyperlipidemia will be studied in the chick liver model system. The characterization of the physical nature of the nuclear form of the estrogen receptor and its interactions with nuclear components, particularly the nuclear matrix, will be investigated. The control of transcription of the apoVLDL II gene will be studied using specific cDNA probes. The presence of high molecular weight precursors to apoVLDL II mRNA and their processing will be studied. The nuclear matrix will be characterized by biochemical and morphological methods. Attempts will be made to determine the role of the nuclear matrix in steroid hormone action.