Characterization of plasma membrane lipids and luteinizing hormone receptors of ovine corpora lutea during luteolysis and early pregnancy

Oleic acid in the modulation of oocyte and preimplantation embryo development

Potential reproductive effects are considered as the major aspect of biomolecules functionality in an organism. The recent identification of differential patterns of fatty acids across ovarian follicles and their association with levels of sexual maturity highlights the importance of these biomolecules. It is well known that fatty acids are highly diverse in terms of their functional properties. Oleic acid is chemically classified as an unsaturated omega-9 fatty acid. Besides serving as an important energy source, oleic acid is involved in metabolic and structural roles. Free and esterified oleic acids are compartmentalized into discrete extracellular fluids, cell organelles and found within the cytosol. This review summarizes the current knowledge on the contribution of oleic acid in regulating female fertility, particularly its involvement in female germ cell growth and development. Oleic acid has been identified as a blastomeric and post-cryopreservation survival biomarker in bovine. Several related studies have shown the critical role of oleic acid in counteracting the detrimental effects of saturated fatty acids and in paracrine support of oocyte development. Although available data are not ideally detailed, most data suggest that oleic acid can contribute to normal oocyte and preimplantation embryo development via mechanisms involving metabolic partitioning of fatty acids, change in the membrane structural organization, attenuation of oxidative stress and regulation of intracellular signalling. Thus, oleic acid may play a significant role in oocyte and early embryo development, suggesting that future studies should explore in more detail its potential effects on the physiopathology of female reproduction.

Pregnancy-associated genes contribute to antiluteolytic mechanisms in ovine corpus luteum

The hypothesis that ovine luteal gene expression differs due to pregnancy status and day of estrous cycle was tested. RNA was isolated from corpora lutea (CL) on days 12 and 14 of the estrous cycle (NP) or pregnancy (P) and analyzed with the Affymetrix bovine microarray. RNA also was isolated from luteal cells on day 10 of estrous cycle that were cultured for 24 h with luteolytic hormones (OXT and PGF) and secretory products of the conceptus (IFNT and PGE2). Differential gene expression (>1.5-fold, P < 0.05) was confirmed using semiquantitative real-time PCR. Serum progesterone concentrations decreased from day 12 to day 15 in NP ewes (P < 0.05) reflecting luteolysis and remained >1.7 ng/ml in P ewes reflecting rescue of the CL. Early luteolysis (days 12-14) was associated with differential expression of 683 genes in the CL, including upregulation of SERPINE1 and THBS1. Pregnancy on day 12 (55 genes) and 14 (734 genes) also was associated with differential expression of genes in the CL, many of which were ISGs (i.e., ISG15, MX1) that were induced when culturing luteal cells with IFNT, but not PGE2. Finally, many genes, such as PTX3, IL6, VEGF, and LHR, were stabilized during pregnancy and downregulated during the estrous cycle and in response to culture of luteal cells with luteolytic hormones. In conclusion, pregnancy circumvents luteolytic pathways and activates or stabilizes genes associated with interferon, chemokine, cell adhesion, cytoskeletal, and angiogenic pathways in the CL.

Luteotropic and luteolytic mechanisms in the bovine corpus luteum

The function of the corpus luteum (CL) is a key element in many reproductive processes including ovulation, length of the estrous cycle, recognition of pregnancy and embryo survival in all mammalian species. The main function of the CL is to produce progesterone which acts on its tissues to prepare them for successful pregnancy. The CL is controlled by numerous biological compounds which provide luteotropic support during the estrous cycle and pregnancy and for inducing luteolysis at the end of the cycle The purpose of this paper is to review the mechansims responsible for controlling the endocrine function of this tissue in the bovine ovary.

Immunochemical characterization and cellular distribution of protein kinase C isozymes in the bovine corpus luteum

Research was conducted to determine the nature of the isoforms of protein kinase C (PKC) present in the bovine (Bos taurus) corpus luteum (CL) and their subcellular distribution. Western blot analysis was performed using isozyme-specific polyclonal antibodies and revealed that the bovine corpus luteum contains the alpha and epsilon isozymes of PKC, but not the beta, gamma, delta or zeta isozymes. Subcellular fractionation demonstrated that the alpha and epsilon isozymes of PKC were present in both the cytosolic and plasma membrane fractions. Densitometric measurements of Western blots of the subcellular luteal PKC fractions indicated that PKC alpha was found predominantly in the cytosolic fraction, whereas the majority of PKC epsilon was associated with the plasma membrane.

Unique metabolites of eicosapentaenoic acid interfere with corpus luteum function in the ewe

Experiments were conducted to determine the in vivo and in vitro effects of metabolites of eicosapentaenoic acid on ovine luteal function. Injection of 750 micrograms methyl eicosapentaenoic acid (EPA) or methyl 12(R),13(S)-dihydroxyeicosapentaenoic acid (12,13-diHEPE) into the ovarian artery of ewes on day 10 of the estrous cycle caused a reduction in serum concentrations of progesterone by 48 h posttreatment compared with levels of this steroid in arachidic acid-treated controls (p < 0.005). Although mean serum concentrations of progesterone in methyl EPA-treated ewes during the remainder of the cycle did not differ from those in control ewes, levels in methyl 12,13-diHEPE-treated ewes remained significantly suppressed. Duration of the estrous cycle did not differ among treatment groups (p > 0.05), but more of the methyl 12,13-diHEPE-treated animals (3/5) had exhibited estrus within 3 days after injection than methyl EPA-treated (1/5) or control ewes (0/5). Slices of corpus luteum removed from ewes on day 10 of the estrous cycle were incubated with arachidic acid (controls), 12,13-diHEPE or docosatetraenoic acid (DTA). Regardless of fatty acid treatment, all tissues retained the ability to produce basal levels of progesterone during subsequent incubation. Luteal slices previously exposed to arachidic acid or DTA exhibited an increase in progesterone production in response to subsequent treatment with LH (p < 0.05). In contrast, luteal slices incubated with 12,13-diHEPE did not respond to LH with a significant increase in production of this steroid above that observed in controls. All tissues displayed a marked increase in progesterone synthesis upon treatment with 8-Br-cAMP relative to incubation of tissue alone (p < 0.001). Subcellular distribution of [14C]-12,13-diHEPE in luteal cells after incubation revealed that the majority of the fatty acid was associated with the plasma membrane. These data suggest that metabolites of eicosapentaenoic acid with hydroxyl groups on adjacent carbon atoms interfere with luteal function in the ewe, perhaps in part by altering luteal response to LH.

Membrane fractions display different lipid and enzyme content in three cell types in 16-cell stage embryos of sea urchins

Three cell types were isolated from dissociated 16-cell sea urchin embryos. Four membrane density fractions from discontinuous gradients have different proportions of lipids, surfacer markers and enzymes for the three cell types. Assays of lipid content, CH/PLIPID and SPH/PC ratios, acyl chain length, level of unsaturation by proton NMR and assays of enzyme activity revealed variation at the same density between the three cell types and among different densities from one cell type. There were also differences between whole embryos and dissociated embryo cells. There was no typical membrane domain at a particular density common to the cell types. Cell surface characteristics and polarity of adult cells rely on which lipid domains and enzymes are present, their association with cytoskeleton and how they are localized. At the 16-cell stage these characteristics are still very dynamic as revealed by cytochemical localization of Na+/K(+)-ATPase which varied with cell type and suggests endocytosis at set times in the division cycle. Polarity has not been permanently set for Na+/K(+)-ATPase yet. Membrane enzyme and lipid distributions unique to the three cell types seen in this study suggest parcelling out or insertion of new membrane domains occurs during early sea urchin cleavage. Perturbation of membrane density distribution and lipid content occurs after treatment of embryos with animalizing and vegetalizing teratogens which alter development.