 |
 |
------------------------------------------------------------------------- Mechanism By Which Progesterone Protects Against Heart Disease Identified ------------------------------------------------------------------------- WESTPORT, Sep 02 (Reuters) - Harvard scientists report in the current issue of Nature Medicine that progesterone protects against cardiovascular disease through direct inhibition of DNA synthesis in smooth muscle cells, which blocks the proliferation of arterial smooth muscle cells, a major factor in formation of atherosclerotic plaque. The research team that reports this finding is the same that first reported three years ago that elevated homocysteine levels are linked to heart disease. Principal author Dr. Edgar Haber says that he and his colleagues analyzed the action of progesterone receptors in smooth muscle cells and found that the hormone directly blocks DNA synthesis in a dose-dependent manner. They also discovered that pretreatment of rat aorta with the progesterone antagonist RU486 blocks progesterone's inhibitory action. The Boston team analyzed both human and rat aortic smooth muscle cells in vivo and in vitro. They observed that levels of cyclin A and E mRNA decline in the presence of progesterone, which suggests that the hormone interrupts the cell cycle at the G1/S transition; that progesterone inhibits [3H]thymidine incorporation into the cell, which is an indication of a stop in DNA synthesis; and that progesterone causes a decrease in the growth rate of smooth muscle cell proliferation. Dr. Haber notes in his conclusion that the relative risk of coronary artery disease in postmenopausal women who take both estrogens and progestins as hormone replacement therapy is 0.39. The relative risk in age-matched women who take estrogens alone is 0.60. The relative risk in women who are not on hormone replacement therapy is 1.0. Nature Medicine 1997;3:000-000. Copyright 1997 Reuters Limited. <http://www.reutershealth.com/news/docs/199709/19970902scd.html> ------------------------------------------------------------------------- [log in to unmask]