Abstract
To elucidate the physiological roles during pregnancy of vascular endothelial growth factor (VEGF), we examined the temporal and spatial expression of VEGF protein and mRNA in the rat uterine and placental tissues throughout pregnancy. The uterine tissue of nonpregnant rats, pregnant rats, and the rat placental tissue were examined by Northern blotting, in situ hybridization and immunohistochemistry. Northern analysis revealed the existence of VEGF mRNA in the uterus and placenta regardless of the stage of estrous cycle or pregnancy. The results of in situ hybridization and histochemistry for nonpregnant rat specimens showed that VEGF mRNA and protein accumulated in myometrial smooth muscle cells, glandular epithelial cells, stromal cells, and endometrial epithelial cells during each stage of the estrous cycle. The level of accumulation increased in all but the myometrial smooth muscle cells on estrus, and further increased during pregnancy. Furthermore fetal compartments such as trophoblasts, trophoblast giant cells, vitelline epithelial cells, and amnion were labeled more strongly than the maternal compartment.
In conclusion, the spatial expression of VEGF was relatively constant in rat maternal uterus during the estrous cycle and during pregnancy; however, there was a temporal change of VEGF expression.
