Effect of prostaglandin F2 alpha on Na+-K+-ATPase activity in luteal membranes

Detrimental effects of prostaglandin F2α on preimplantation bovine embryos

Two studies were performed to determine effects of prostaglandin F2alpha (PGF2alpha) on continued development of pre-compacted (in vitro-produced) and compacted (in vivo-derived) bovine embryos. In Experiment 1, pre-compacted embryos were placed in KSOM media supplemented with polyvinyl alcohol (0.3%) and assigned to the following treatments: (1) control; (2) PGF-1 (1 ng/mL PGF2alpha); (3) PGF-10 (10 ng/mL PGF2alpha); (4) PGF-100 (l00 ng/mL PGF2alpha); or (5) PGE-5 (5 ng/mL PGE2). Following 4 days of incubation in assigned treatments, continued development of pre-compacted embryos to blastocysts was reduced by addition of PGF2alpha in culture medium (P = 0.002). Development did not differ between control and PGE2 treatments (P > 0.10). In Experiment 2, compacted morula' s were placed in KSOM-PVA supplemented media and assigned to one of four treatments: (1) control; (2) PGF-0.1 (0.1 ng/mL PGF2alpha); (3) PGF-1 (1 ng/mL PGF2alpha); and (4) PGF-10 (10 ng/mL PGF2alpha). After 24h in culture, embryos were washed and placed in KSOM-BSA (0.5%) without PGF2alpha for an additional 48 h until assessment for development. Continued development of compacted morula to blastocyst was not affected by addition of PGF2alpha to the culture medium (P > 0.10). However, hatching rates of embryos cultured with PGF2alpha were lower (P = 0.05). In conclusion, it is suggested that PGF2alpha has a direct negative effect on continued embryonic development of pre-compacted and compacted bovine embryos.

Mechanisms of sodium pump regulation

The Na(+)-K(+)-ATPase, or sodium pump, is the membrane-bound enzyme that maintains the Na(+) and K(+) gradients across the plasma membrane of animal cells. Because of its importance in many basic and specialized cellular functions, this enzyme must be able to adapt to changing cellular and physiological stimuli. This review presents an overview of the many mechanisms in place to regulate sodium pump activity in a tissue-specific manner. These mechanisms include regulation by substrates, membrane-associated components such as cytoskeletal elements and the gamma-subunit, and circulating endogenous inhibitors as well as a variety of hormones, including corticosteroids, peptide hormones, and catecholamines. In addition, the review considers the effects of a range of specific intracellular signaling pathways involved in the regulation of pump activity and subcellular distribution, with particular consideration given to the effects of protein kinases and phosphatases.

Changes in superoxide radical formation, lipid peroxidation, membrane fluidity and cathepsin B activity in aging and spawning male Chinook salmon (Oncorhynchus tschawytscha)

Superoxide radical (SOR) formation in the brain and the liver of male Chinook salmon (Oncorhynchus tschawytscha) increased in mitochondrial and plasma membrane samples as they aged. In 2-year-old salmon, spawning also lead to a significant elevation in SOR formation in mitochondrial and plasma membrane samples. The rise in this free radical was associated with an increase in lipid peroxidation, a decrease in plasma membrane fluidity, and an elevation in cathepsin B activity in the brain and liver. In 2-year-old spawning salmon, the changes in these parameters was greater than in 2-year-old non-spawning salmon. These observations suggest that free radical levels increase with aging and during spawning and indicate that these changes may be involved in cellular degeneration. In addition, these results support the suggestion that cellular degeneration accelerates during the spawning process.

Oxygen radicals and the control of ovarian corpus luteum function

The superoxide radical (SOR) and other reactive oxygen species form in cells during the course of respiration as well as in response to various stimuli. Although well known for their damaging effects, these agents can also work beneficially to control cell function. The present review examines the evidence that oxygen radicals and H2O2 may regulate steroid hormone biosynthesis in the ovarian corpus luteum. Recent findings indicate that luteal cells can employ reactive oxygen species at specific sites in controlling the production of progesterone over the course of the reproductive cycle and in inhibiting its synthesis during regression at the end of the cycle. These studies indicate that oxygen radicals and related compounds may function as intracellular regulators of steroidogenesis in the corpus luteum.

Treatment of sheep with prostaglandin F2 alpha enhances production of a luteal chemoattractant for eosinophils

Eosinophils were quantitated in sections of luteal tissue obtained from sheep treated with a luteolytic dose of prostaglandin (PG) F2 alpha. Increased numbers of cells were detected before the onset of either functional (decline in sera or tissue concentrations of progesterone) or morphological regression. Luteal tissue was shown to produce a specific chemoattractant for eosinophils as assessed by a linear under-agarose migration assay. Eosinophils were responsive toward leukotriene B4, but not toward PGF2 alpha or a synthetic N-formyl peptide. Because eosinophils are capable of mediating tissue damage in immune/inflammatory conditions, it is suggested that these cells could play a similar role in the mechanics of luteolysis.