Menstrual cycle and sensitivity of human fallopian tube to prostaglandins

The shapes and frequencies of spontaneous contractions of circular muscle strips of the human oviduct differ during the menstrual cycles. However, under given conditions, the frequency and amplitude of the contractions were continuously reduced during perfusion with Krebs solution. In the presence of prostaglandin (PG) synthesis inhibitors or an antagonist, a gradual and continuous reduction was no longer observed, and low concentrations (10(-15)-10(-10) M) of PGE2 markedly suppressed the amplitude and frequency of the spontaneous contractions. The highest sensitivity of smooth muscle cells to PGE2 was observed during the periovulatory phases. Spontaneous prepotentials followed by slow waves were observed, and the latter potentials triggered contraction of the tissue. PGE2 (10(-14)-10(-12) M) inhibited, and PGF2 alpha (10(-9)-10(-7) M) enhanced the frequency of these slow waves. The amount of PGE series released from the tissues was twice of PGF series. These results suggest that endogenous prostaglandins play a physiological role in the transport of ovum in the human fallopian tube as a result of the regulation of spontaneous membrane and mechanical activities.