Cytoplasmic and nuclear progesterone receptors in human fallopian tube and their relationship to plasma steroids during the menstrual cycle.

Progesterone (P) binding sites in the ampullary and isthmic regions of the fallopian tube and corpus myometrium were measured during the follicular, ovulatory, and luteal phases. Both cytosolic and nuclear fractions were used for P receptor determination. The concentrations of P receptors were similar in the isthmus and myometrium in all three phases. Although the absolute concentration of nuclear P receptor was always lower than that of the cytosolic receptor, the overall pattern of receptor concentration in the different regions was the same, being highest in the ampulla. Both cytosolic and nuclear receptor concentrations in all tissues were lowest in the luteal phase and highest in the ovulatory phase. In all tissues examined in the luteal phase the cytosolic P receptor but not the nuclear receptor was inversely related to plasma P concentration. The data are compatible with a dual control of P receptors by estrogen and P.