Pre-menopausal women appear to have a natural protection from heart attack which is lost after menopause. One current hypothesis is that this protection is attributable to the sex steroids, in particular to estrogens, possibly working with other factors on vascular cells. Vascular smooth muscle cells are responsible for production of the bulk of the connective tissue protein in major arteries. Smooth muscle cell invasion into the lumen of an artery and resulting connective tissue proliferation has been implicated in the pathogenesis of atherosclerosis. Previous studies have shown that these smooth muscle cells in culture are similarly capable of synthesizing collagen, predominantly types I and III and lesser amounts of basement membrane collagen, as well as elastin and glycosaminoglycans. Administration of estrogens to animals lowers the production of collagen by vascular smooth muscle cells. Recently, we observed that treatment of these cells in culture with estradiol causes a similar reduction in the quantity of procollagen produced. To further elucidate the mechanisms of the estradiol effect, we plan to monitor three components of collagen produced in rabbit vascular cell cultures: the intracellular soluble procollagens, the extracellular souluble collagens in the medium and the extracellular insoluble collagen incorporated into the matrix. Distributions of the various collagen types in each of these compartments will be assessed. Experiments will be performed to distinguish between transcriptional, pre-translational and post-translational levels of control. Collagen mRNA will be monitored by employing a cell-free translation system as well as by hybridization to cDNA clones specific for the individual collagen chains. These values will be compared to the rate of transcription of the various mRNA species, and we will seek to correlate these with alterations inthe chromatin structure of collagen type I and type III genes. Since, in preliminary studies, estradiol was found to alter the overall architecture of the chromatin in smooth muscle cells, general structural and functional evaluation of the chromatin will also be performed.