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Placental Biosynthesis, Metabolism, and Transport of Eicosanoids
Published in Murray D. Mitchell, Eicosanoids in Reproduction, 2020
The first reports of PGs within the human placenta naturally concentrated on the classical primary prostaglandins, E2 and F2α. In a study of the distribution of these compounds throughout the feto-placental unit, Willman and Collins1 found no difference in the concentrations of PGE2 and F2α in placental homogenates measured by RIA during the first trimester, at term, or during labor. Concentrations of PGE2 appeared to be always greater than F2α, but the concentration of both in placental tissue was less than that in the endometrium, myometrium, amnion, and chorion. The biosynthesis of PGE2 from [14C]arachidonic acid by placental villous tissue homogenates was demonstrated by Kinoshita et al.,2 who confirmed that there was less activity in villous tissue than in the decidua or amnion. Similarly, Duchesne et al.3 showed that the microsomal pellet of placenta would synthesize PGE2 from [14C]arachidonic acid, but that there was less enzyme activity than in the corresponding fetal membranes (1 to 3% conversion in placenta vs. 5 to 8% conversion in membranes). In these experiments, 15-keto-PGE2 was found, demonstrating the presence of prostaglandin dehydrogenase (PGDH) activity in the preparation. The same workers4 found that PGE2, TXB2, and 6-keto-PGF2α (the hydrolysis products of TXA2 and prostacyclin, respectively) could be measured by RIA in homogenates of the human placenta and that the homogenates converted radiolabeled PG endoperoxide PGH2 to PGE2 via PGE2 isomerase. When subcellular fractions were employed, placental microsomes were able to convert PGH2 to TXA2 and 12-hydroxyheptadecatrienoic acid (12-HHT), a finding confirmed by gas chromatography/mass spectrometry and by inhibition of synthesis by the TX synthase inhibitor imidazole. The cytosol fraction converted PGH2 to PGD2, but was also found to contain a heat-stable factor which inhibited TXA2 synthesis when added to microsomes and thus shifted PGH2 metabolism to PGE2. Interestingly, no conversion of PGH2 to PGI2 or PGF2α was seen in any subcellular fraction. This work illustrated the differential subcellular localization of the biosynthetic enzymes and the presence of inhibitory components that can affect product formation in the intact cells. Later, these workers5 again demonstrated no synthesis of 6-keto-PGF2α from either radiolabeled [14C]arachidonic acid or PGH2 by placental tissue fragments, homogenates, cytosol, or microsomes, nor did the biosynthesis of 6-keto-PGF2α appear to be inhibited by the presence of free radicals in the placenta.
Sample management for clinical biochemistry assays: Are serum and plasma interchangeable specimens?
Published in Critical Reviews in Clinical Laboratory Sciences, 2018
Gabriel Lima-Oliveira, Denis Monneret, Fabrice Guerber, Gian Cesare Guidi
In Table 3, we did not observe a difference (p > .05) between serum and plasma for total cholesterol or triglycerides; however, HDL cholesterol was higher in serum compared to plasma. Moreover, the mean percent difference between HDL cholesterol in serum and in plasma from blood collected in Sarstedt® tubes could jeopardize the evaluation of cardiovascular disease risk and therapeutic decisions (Figure 3). Furthermore, laboratory managers should carefully consider selecting plasma or alternatively serum for some lipid metabolite assays viewed as risk biomarkers, such as:the metabolites involved in platelet aggregation (e.g. thromboxane B2, 12-hydroxyheptadecatrienoic acid, and 12-hydroxyeicosatetraenoic acid) need to be measured using plasma because the clotting process causes large increases in these metabolite levels, which do not reflect their true levels [94];12-hydroxyeicosapentaenoic, 14-hydroxy docosahexaenoic acid, and 20-hydroxy- Leukotriene B4 can be detected only in serum compared with plasma, as plasma levels are below detection limit [94];lysophosphatidylinositol is more abundant in plasma than in serum, possibly because their consumption is prevented in plasma by inhibition of the blood clotting cascade that activates thrombin and other proteases [95].
DHA but not AA Enhances Cisplatin Cytotoxicity in Ovarian Cancer Cells
Published in Nutrition and Cancer, 2018
Alicja Zajdel, Magdalena Kałucka, Ewa Chodurek, Adam Wilczok
On the other hand, AA, its metabolites, and their receptors may promote ovarian cancer progression (10,11). The expression of leukotriene B4 receptors BLT1 and BLT2 in ovarian cancer tissues is found to be increased at the advanced cancer stages and correlates with a poor clinical outcome (12,13). BLT2 is a receptor for several eicosanoids derived from AA such as leukotriene B4 (LTB4), 12-hydroxyeicosatetraenoic acid (12(S)-HETE), and 12-hydroxyheptadecatrienoic acid (12-HHT) (10,12). Recent studies suggest that LTB4, a major ligand responsible for BLT2 stimulation, plays a crucial role in mediating cisplatin resistance in ovarian cancer (14).