Pregnant mice submitted to Surgical Embryo Euthanasia (SEE) induce loss of expression of inducible nitric oxide synthase isoform and NO concentration in the maternal-fetal interface

The well-succeeded pregnancy in humans and rodents is the consequence of close interaction between maternal and fetal cells with intervening of cytokines and chemical mediators. In this process a pregnant uterus subset NK cells - uterine Natural Killer cells (uNK cells) play a pivotal modulatory role under the influence of local physiological hypoxia and other alterations. The aim of the present work was to evaluate the expression and commitment of induced form of nitric oxide synthase (iNOS) and NO concentration in the homeostasis of pregnant uterus. It was used normal pregnant mice on gd 10th and those submitted to surgical intervention to induce mechanical lesion in the embryos (SEE). Uterine samples were collected at 0.5, 1, 2 and 6 h after embryo lesion and processed for paraffin embedding and tissue homogenate. The samples destinate for paraffin embedding was performed the Dolichos biflorus (DBA) lectin cytochemistry and anti-iNOS immunocytochemistry. The samples destinate to tissue homogenates were processed for SDS-PAGE and Western-blot using anti-iNOS and evaluate of NO concentration. The embryo-injured uterine segments showed hyperemia and hemorrhage at mesometrial region in which the DBA lectin reaction showed altered uNK cells suggesting the degranulation. Positive reaction with anti-iNOS was seen on uNK cells, trophoblast giant cells, endometrial stromal and decidual cells and smooth muscle cells in the normal pregnant uterus, but 1 and 2 h after embryo lesion, the iNOS labeling decreased or was absent only in uNK cells. The same results was obtained with NO concentration. These results confirm the unique constitutive expression of iNOS in the pregnant mice uterus, being the uNK cells the only one responsive against stress of embryo failure, besides showing that excessive NO produced by quick activation of uNK-iNOS should affect the local vascular permeability.