STEROID-HORMONE REGULATION OF MYOSIN SUBUNIT EXPRESSION IN SMOOTH ANDCARDIAC-MUSCLE

We investigated the effects of ovarectomy and the steroid hormones est rogen and testosterone on the in vivo expression of heavy (MHC) and li ght (MLC) chains of myosin in the heart, uterus, and aorta of rats. In the heart, ovarectomy decreased alpha-MHC expression, while both ster oid hormones normalized it. Differential steroid hormone effects could be observed on myosin subunit expression of smooth muscle. Testostero ne but not estrogen normalized the ovarectomy-induced decreased expres sion of SM1 and strongly increased the expression of 5'-inserted MHC i n the uterus. Estrogen but not testosterone normalized the ovarectomy- induced diminished MLC17a expression. in contrast to the uterus, no st eroid hormone effects on myosin subunit expression could be observed i n the aorta. (C) 1995 Wiley-Liss, Inc.