The distribution of immunocytes in the rat uterus undergoes profound changes during early pregnancy. This study was designed to evaluate the respective contributions of hormonal and local factors to regulation of the distribution and number of MCA341+ monocyte-macrophage antigen-bearing cells and T-lymphocyte-polymorphonuclear leukocyte (PMN) antigen-bearing cells before and during implantation of the fertilized ovum. Immunohistological data in normal rat pregnancy were compared to those found in cycling rats, ovariectomized rats, pseudopregnant rats (the oviducts of which had been sectioned on Day 0.5 of pregnancy), and pregnant rats injected with the antiprogesterone RU-486 on Day 0.5 of pregnancy. Four major events were observed: (1) transient accumulation of T-lymphocyte-PMN antigen-bearing cells in the endometrium close to the lumen and occurring only in the pregnant state 12 h after mating; (2) accumulation of an MCA341+ antigen-bearing monocyte-macrophage subset in the uterus, especially the luminal endometrium, 12 h after ovulation in pregnant as well as cycling rats; (3) progressive disappearance of these labeled cells starting 1 day after ovulation in the pregnant and nonpregnant states and influenced by RU-486 injection; (4) relative persistence of labeled cells in the deep endometrium before the implantation of the conceptus--which requires the presence of fertilized ovum in the genital tract. In conclusion, a complex multifactorial and sequential control of the distribution and number of cells bearing MCA341+ monocyte-macrophage or T-lymphocyte antigens appears to be at work before and during implantation of the rat conceptus, and may involve hormonal factors as well as local factors produced by the embryo or trophoblastic cells.
Amnion and chorion cells from human fetal membranes have been cultured. Chorionic cells secrete renin whereas amnionic cells do not. Renin is secreted by chorionic cells as an inactive form that can be activated by trypsin treatment or acid dialysis. The antigenic and enzymatic properties of activated chorionic renin and kidney renin are similar. Incorporation of [35S]methionine in the culture demonstrates that chorionic renin is secreted as a high molecular weight form, 54K. This 54K inactive renin could represent the proenzyme.
Injection of PAF into the left uterine horn induced a dose-dependent decidua-like reaction in the pseudopregnant rat. This reaction was maximal when PAF was injected at Day 5 of pseudopregnancy and was blocked by the specific PAF antagonist, BN 52021. BN 52021 did not interfere with the decidual reaction induced by prostaglandin E-2 or insertion of a cotton thread in the uterine horn. In contrast, a decidua-like reaction was not evoked by the inactive lyso-PAF, demonstrating the specificity of the action of PAF. The decidua-like reaction induced by PAF involves the generation of cyclooxygenase metabolites of arachidonic acid since it was inhibited by indomethacin. The histological alterations induced by PAF were similar to those observed after embryo implantation, strengthening the postulate for a role of the autacoid in the early stages of pregnancy.
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