Nitric oxide synthase activity in human trophoblast, term placenta and pregnant myometrium

To investigate the possible role of nitric oxide (NO) produced locally or intramurally in the quiescence of the pregnant myometrium, nitric oxide synthase (NOS) activity was measured in samples from first trimester (villous, and non villous-trophoblast), term placenta and pregnant myometrium. Trophoblast tissue was obtained from psychosocial termination of pregnancy (9 – 12 weeks' gestation) whereas placenta and myometrium, from the same patient, at deliveries by Caesarean section. NOS activity was measured in both cytosolic and particulate fractions by the formation of (14)C-citrulline from (14)C-arginine. Western immunoblotting was used to identify the endothelial NOS (eNOS) and neuronal (nNOS) isoforms. The activity of NOS in particulate fractions from all preparations was considerably higher than the cytosolic fractions. Activity in all fractions except the myometrium was highly Ca-dependent. More than 50% of particulate NOS from the myometrium was Ca-independent. NOS activity was highest in the villous trophoblast and there was a significant difference between the villous and non-villous trophoblast. In placenta and myometrium, NOS was 2–4 fold and 20–28-fold lower than the villous trophoblast, respectively. Western blot analysis showed clearly eNOS in the particulate fraction and a weak eNOS band in the cytosolic fractions, whereas nNOS was not detectable in any of the fractions. In view of the marginal activity of NOS in the myometrium, NO produced by the trophoblast and placenta could play a significant role in maintaining uterine quiescence by paracrine effect

Important differences in nitric oxide synthase activity and predominant isoform in reproductive tissues from human and rat

For the extrapolation of data obtained from experimental animals to the human situation, it is important to know the similarities and differences between human and animal species. Some important characteristics of nitric oxide synthase (NOS) in myometrium and vagina from human and rat were compared. NOS-activity was measured by the formation of (14)C-citrulline from (14)C-arginine and the expression of NOS isoforms was examined by Western blotting. NOS activity in human uterus and vagina was significantly lower than in the tissues from rat. In contrast to the rat where NOS activity was predominantly found in the cytosolic fractions, NOS activity in particulate and cytosolic fractions from both human myometrium and vagina was similar. Data from Western blots confirmed that eNOS and nNOS isoforms were concentrated in the particulate and cytosolic fractions, respectively. Estrogen treatment of rats resulted in a down regulation of uterine cytosolic NOS activity. A down regulation of NOS in the cytosolic fraction was also seen in the human pregnant myometrium as compared with the nonpregnant myometrium. The vaginal NOS activity was considerably higher than the uterus in both species. In spite of some clear-cut qualitative and other differences between human and rat tissues, there are some interesting similarities. Downregulation in pregnancy of human uterine NOS is probably due to, at least in part, the influence of estrogen and progesterone

Effect of Carbamate Insecticide, Lannate, on the Gonads of Mice

The effect of the carbamate insecticide, lannate, on the gonads of mice was studied. Treating mice with lannate at a dose level of 10mg/kg body weight daily for 3-6 weeks had induced degenerative effects in the gonads, as follows, first in testis, a significant reduction in the diameter of the seminiferous tubules and germinal epithelial height. Histological examination of the testis showed that the seminiferous tubules were elongated and contained reduced spermatogenic cells. The number, of mature sperms was markedly reduced and after 3 weeks the sperm bundles were completely absent. On the other hand, the effect on the ovarian structure showed that, decrease in the number of secondary ovarian follicles and corpora lutea was recorded, while, the number of atretic follicles showed a significant increase. It is speculated that it may be resulted from the inhibition of RNA synthesis due to the effect of lannate

Effect of Carbamate Insecticide, Lannate, on the Gonads of Mice

The effect of the carbamate insecticide, lannate, on the gonads of mice was studied. Treating mice with lannate at a dose level of 10mg/kg body weight daily for 3-6 weeks had induced degenerative effects in the gonads, as follows, first in testis, a significant reduction in the diameter of the seminiferous tubules and germinal epithelial height. Histological examination of the testis showed that the seminiferous tubules were elongated and contained reduced spermatogenic cells. The number, of mature sperms was markedly reduced and after 3 weeks the sperm bundles were completely absent. On the other hand, the effect on the ovarian structure showed that, decrease in the number of secondary ovarian follicles and corpora lutea was recorded, while, the number of atretic follicles showed a significant increase. It is speculated that it may be resulted from the inhibition of RNA synthesis due to the effect of lannate

Vasodilator factors in the systemic and local adaptations to pregnancy

We postulate that an orchestrated network composed of various vasodilatory systems participates in the systemic and local hemodynamic adaptations in pregnancy. The temporal patterns of increase in the circulating and urinary levels of five vasodilator factors/systems, prostacyclin, nitric oxide, kallikrein, angiotensin-(1–7) and VEGF, in normal pregnant women and animals, as well as the changes observed in preeclamptic pregnancies support their functional role in maintaining normotension by opposing the vasoconstrictor systems. In addition, the expression of these vasodilators in the different trophoblastic subtypes in various species supports their role in the transformation of the uterine arteries. Moreover, their expression in the fetal endothelium and in the syncytiotrophoblast in humans, rats and guinea-pigs, favour their participation in maintaining the uteroplacental circulation. The findings that sustain the functional associations of the various vasodilators, and their participation by endocrine, paracrine and autocrine regulation of the systemic and local vasoactive changes of pregnancy are abundant and compelling. However, further elucidation of the role of the various players is hampered by methodological problems. Among these difficulties is the complexity of the interactions between the different factors, the likelihood that experimental alterations induced in one system may be compensated by the other players of the network, and the possibility that data obtained by manipulating single factors in vitro or in animal studies may be difficult to translate to the human. In addition, the impossibility of sampling the uteroplacental interface along normal pregnancy precludes obtaining longitudinal profiles of the various players. Nevertheless, the possibility of improving maternal blood pressure regulation, trophoblast invasion and uteroplacental flow by enhancing vasodilation (e.g. L-arginine, NO donors, VEGF transfection) deserves unravelling the intricate association of vasoactive factors and the systemic and local adaptations to pregnancy

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Effects of tamoxifen and estradiol on estrogen binding sites in the urogenital tract: an experimental study in the rabbit

The aim of the study was to investigate the effects of estradiol and tamoxifen alone and in combination on the estrogen binding site status of the urogenital tract in the rabbit. Bilaterally ovariectomized rabbits were divided into four groups of six. Wereas the control group received no treatment, the remaining rabbits were treated with estrogen orland tamoxifen. Cytosolic and nuclear fractions were isolated from the uterus, vagina, urethra and urinary bladder and used for binding site assay, by radioligand binding. The total weight of the rabbit vagina and uterus was increased significantly by both estradiol, tamoxifen and the combination of the two. The total weight of the urethra was increased only in the combination group. The cytosol binding site was downregulated by estradiol, tamoxifen and combination in the uterus, and in the vagina. Cytosol binding site in the urethra was not detected. The combination of estrogen-tamoxifen markedly reduced the nuclear binding site in the urethra and decreased affinity of the nuclear binding sites in all three tissues. The data suggest that tamoxifen has a specific ability to modulate the transcriptional activity of the estrogen binding sites in the rabbit urogenital tract