Intraperitoneal admnistration of estradiol dipropionate (EDDP) leads to membrane hypopolarization, the growth of its resistance, reduction of cell excitation and potassium and sodium ions redistribution on both sides of the membrane. In old animals the shift of the membrane potential occurred in response to half estrogen doses (50 μg) in comparison with that in adults, this pointing to greater sensitivity of the muscle cells of old rats to EDDP. The protein biosynthesis inhibitors prevented development of hyperpolarization, changes of electrical properties of the membrane and ionic shifts usually following estrogen administration. Elimination of the EDDP effect in old animals was reached with lesser doses of the protein biosynthesis inhibitors.