Variations in the levels of secretory component in human uterine fluid during the menstrual cycle

To determine whether variations in the level of secretory component (SC) occur during the menstrual cycle, we compared the amounts of SC in human uterine secretions during the proliferative, secretory, and menstrual phases. Uterine washes were obtained from women (ages: 18-49) with histologically normal endometria by lavage with Gravlee jet wash device using isotonic glycine. SC was measured by a radioimmunoassay which recognizes primarily free SC. Levels of uterine luminal SC, when expressed as the percentage of total wash protein, were highest during the secretory phase, significantly reduced during the proliferative phase and lowest during menstruation. The mean protein concentration in uterine fluids did not vary significantly during the menstrual cycle. Total amounts of SC were also greatest during the secretory phase, averaging two times higher than SC levels in proliferative samples. These results demonstrate that fluctuations do occur in the SC content of human uterine secretions during the menstrual cycle and suggest that hormones play an important role in the secretory immune system of the human uterus.