On the source of uterine 'luminal fluid' proteins in the mouse.

Examination by light-, transmission electron- and scanning electron-microscopy showed that flushing the lumen of the mouse uterus with small volumes of fluid damaged the endometrium by rupturing and removing luminal epithelial cells, splitting the epithelial basement membrane and connective tissue stroma, and rupturing and leaching stromal cells and blood vessels. The damage increased with increasing progestation of the uterus and between Days 4 and 5 of pregnancy. I conclude that many so-called 'luminal fluid' proteins originate from luminal and stromal cells, intercellular fluid and blood and that apparent changes in luminal fluid protein content during early pregnancy may largely reflect alterations in the extent and type of damage produced by flushing, as a consequence of changes in the physical state of the uterus induced by hormones and the presence of blastocysts.