Changes in physiological properties of rabbit oviduct by ovarian steroids

Effects of estrogen and progesterone on electrical and mechanical properties of longitudinal smooth muscle cells of the rabbit fallopian tubes were investigated using microelectrode and isometric tension recording methods. In tissues from the estrogen-treated rabbits, there was a decrease in frequency of spontaneous contractions, whereas an increase was seen in tissues from the progesterone-treated rabbits. The membrane potential of smooth muscle cells of the fallopian tube was -58.5 mV. Following treatment with progesterone or estrogen, the membrane was either depolarized (-53.7 mV, P less than 0.05) or hyperpolarized (-63.2 mV, P less than 0.05), respectively. Spontaneous burst discharges were recorded from these smooth muscle cells, and changes in the frequency of the bursts induced by treatment with progesterone or estrogen corresponded well with changes in the spontaneous contractions. Passive electrical parameters such as the time and space constants were increased by treatment with progesterone and decreased by treatment with estrogen. Therefore endogenous ovarian steroids probably participate in transport of the ovum by controlling spontaneous membrane and mechanical activities of the smooth muscle cells of the fallopian tube.