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Cd2+ has been associated with decreased sperm motility in individuals exposed to this element, such as smokers. Among other factors, this lowered motility could be the result of inhibition exerted by Cd2+ on the activity of the sperm ATPases associated with sperm motility. In this study, we evaluated the plasma membrane Ca2+-ATPase and the axonemal dynein-ATPase activities as well as sperm motility, in the presence of different free Cd2+ concentrations in the assay media. It was found that spermatozoa incubated for 5 h in a medium containing 25 nm free Cd2+ showed a significant inhibition of progressive motility, reaching values even lower at higher Cd2+ concentrations. In addition, it was found that the activity of the plasma membrane Ca2+-ATPase reached maximal inhibition at 50 nm free Cd2+, with a K50% inhibition of 18.3 nm free Cd2+. The dynein-ATPase activity was maximally inhibited by 25 nm free Cd2+ in the assay medium, with a K50% inhibition of 11.3 nm Cd2+. Our results indicate that the decreased activity of the sperm ATPases might have a critical importance in the biochemical mechanisms underlying the decreased sperm motility of individuals exposed to Cd2+. [ABSTRACT FROM AUTHOR]

Rhythmic daily changes in the Na,K-ATPase activity have been previously described for rat kidney cortex, showing two peaks: at 0900 h and 2100 h, and two valleys: at 1500 h and 0100 h - 0300 h. The oscillations in Na,K-ATPase activity are produced by an inhibitor, which binds the enzyme and is present in the rat blood plasma at valley times and absent or at very low concentrations at peak times. Since it has been demonstrated that active Na+ extrusion from the cells of several tissues depends not only on the Na,K-ATPase but also on the ouabaininsensitive Na-ATPase, we studied the activity of this latter enzyme of several rat tissues, i.e., kidney cortex, small intestine, liver, heart and red blood cells along the day. None of these tissues showed any variation of their Na-ATPase activity along the day. Preincubation of kidney cortex homogenates obtained at 0900 h, with blood plasma drawn at 0900 h and 1500 h, did not modify the Na-ATPase activity. Our results indicate that the Na- ATPase activity does not oscillate along the day. These results are in agreement with the idea that the Na-ATPase could partially compensate the Na+ transport affected by oscillations of the Na,K-ATPase activity. [ABSTRACT FROM AUTHOR]

In the present work, a Mg [sup 2++] -dependent, Ca [sup 2+] -stimulatedATPase activity was determined and characterized in purified preparationsof syncytiotrophoblast basal (fetal facing) plasma membranes, and its characteristicswere compared to those of the active Ca [sup 2+] -transport already demonstratedin this tissue. Similar to the active Ca [sup 2+] transport, the Ca-ATPaseis Mg [sup 2+] -dependent, is stimulated by calmodulin, and is inhibitedby vanadate. The K[sub m] for Ca [sup 2+] activation is 0.25±0.02µM, a value near to that described for calcium active transportin this tissue. Consequently, the Ca-ATPase activity of human syncytiotrophoblastbasal plasma membrane described in this paper could be responsible for theactive extrusion of calcium from the syncytiotrophoblast toward the fetalcirculation. [ABSTRACT FROM AUTHOR]

Objective: We evaluated the effect of lipid peroxidation on the calcium adenosine triphosphatase activity of red blood cell ghosts from normotensive pregnant women and compared it with the adenosine triphosphatase activity and lipid peroxidation in preeclampsia.Study Design: Ten nulliparous normotensive and 10 nulliparous preeclamptic pregnant women (38 to 39 weeks of gestation) were used as blood donors. Preeclampsia was diagnosed on the basis of blood pressure (>140/90 mm Hg) and proteinuria (>0.5 gm of urinary protein per day). Red blood cell ghosts were prepared for both groups and used for calcium adenosine triphosphatase activity and lipid peroxidation determinations. Control ghosts (normotensive) were irradiated with ultraviolet light for different lengths of time.Results: Calcium adenosine triphosphatase activity of red blood cell ghosts from normotensive women is sensitive to lipid peroxidation. The lipid peroxidation of red blood cell ghosts from preeclamptic women is higher than that from normotensive women.Conclusion: The diminution of the calcium adenosine triphosphatase activity with preeclampsia could be explained by the sensitivity of this adenosine triphosphatase to lipid peroxidation. [ABSTRACT FROM AUTHOR]

Abstract: Several tissues from different animals, including the rat kidney and the freshwater rainbow trout gills, show an ouabain-insensitive, furosemide-sensitive, Na+-stimulated ATPase activity, which has been associated with the active control of the cell volume. This Na-ATPase is Mg2+ dependent and it is inhibited by vanadate, which can be taken as an indication that this enzyme is a P-type ATPase. The P-type ATPases are known to form a phosphorylated intermediate during their catalytic cycle, where the phosphate binds an aspartyl residue at the enzyme''s substrate site. In the current study, we partially characterized the phosphorylated intermediate of the ouabain-insensitive Na-ATPase of rat kidney cortex homogenates and that of gill microsomes from freshwater rainbow trout. While the kidney cortex homogenates, under our assay conditions, show both Na- and Na,K-ATPase activities, the gill microsomes, when assayed at pH 5.2, only show Na-ATPase activity. Both preparations showed a Mg2+-dependent, Na+-stimulated phosphorylated intermediate, which is enhanced by furosemide. Incubation of the phosphorylated enzyme with 0.6 N hydroxylamine (NH2OH) showed that it is acid-stable and sensitive to hydroxylamine, either when phosphorylated in the presence or absence of furosemide. Addition of ADP to the incubation medium drives the reaction cycle of the enzyme backward, diminishing its phosphorylation. Na+ seems to stimulate both the phosphorylation and the dephosphorylation of the enzyme, at least for the Na-ATPase from gill microsomes. In a E1–E2 reaction cycle of the Na-ATPase, furosemide seems to be blocking the transition step from Na·E1∼P to Na·E2-P. [Copyright &y& Elsevier]

Preeclampsia (PE) is a pregnancy-specific syndrome with multisystem involvement which leads to fetal, neonatal, and maternal morbidity and mortality. A model of salt-loaded pregnant rats has been previously studied, sharing several pathological characteristics of preeclamptic women. In this study, it was compared the effects of the treatment with an oral magnesium salt, magnesium gluconate (Mg-gluconate), on the osmotic fragility of red blood cells, lipid peroxidation, and PMCA activity of placental homogenates and red blood cell ghosts in salt-loaded pregnant rats. Mg-gluconate has a higher antioxidant capacity than MgSO 4 due to the presence of several hydroxyl groups in the two anions of this salt. Salt-loaded pregnant rats received 1.8% NaCl solution ad libitum as a beverage during the last week of pregnancy. On day 22nd of pregnancy, the rats were euthanized and red blood cells and placenta were obtained. Salt-loaded pregnant rats showed an increased level of lipid peroxidation and a lowered PMCA activity in placental and red blood cell ghosts, as well as an increased osmotic fragility of their red blood cells. The treatment of the salt-loaded pregnant rats with Mg-gluconate avoids the rise in the level of lipid peroxidation and the concomitant lowering of the PMCA activity of their red blood cell membranes, reaching values similar to those from control pregnant rats. Also, this treatment prevents the increase of the osmotic fragility of their red blood cells, keeping values similar to those from control pregnant rats. Mg-gluconate seems to be an important candidate for the replacement of the MgSO 4 treatment of preeclamptic women., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Rojas, Abad, Piñero, Medina, Chiarello, Proverbio and Marín.)

Magnesium sulfate (MgSO 4 ) has been used as a protector agent for many diseases related to oxidative stress. The effect of MgSO 4 on the oxidized lipid bilayer has not yet been studied using molecular dynamics calculations. In this work, the effects of oxidation were evaluated by using a POPC membrane model at different concentrations of its aldehyde (-CHO) and hydroperoxide (-OOH) derivatives with and without MgSO 4 . Several quantitative and qualitative properties were evaluated, such as membrane thickness, area per lipid, area compressibility modulus, snapshots after simulation finish, density distributions, time evolutions of oxidized group positions, and radial distributions of oxidized group concerning Mg. Results indicate that in the absence of MgSO 4 the mobility of oxidized groups, particularly -CHO, toward the surface interface is high. At a low oxidation level of the bilayer there is an increase in the compressibility modulus as compared to the unoxidized bilayer. MgSO 4 , at a low oxidation level, tends to lessen the oxidation effects by lowering the dispersion in the distribution of oxidized species toward the membrane surface and the water region. However, MgSO 4 does not change the trends of decreasing membrane thickness and area compressibility modulus and increasing area per lipid upon oxidation. In this regard, MgSO 4 diminishes the electrostatic long-distance attractive interactions between the oxidized groups and the charged headgroups of the interface, owing to the Mg +2 and SO 4 -2 screening effects and an electrostatic stabilization of the headgroups, preventing the pore formation, which is well-known to occur in oxidized membranes., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2021 The Author(s).)

Preeclampsia is a heterogeneous pregnancy-specific syndrome associated with abnormal trophoblast invasion and endothelial dysfunction. Magnesium (Mg 2+ ) level may be normal or decreased in women with preeclampsia. However, the use of Mg 2+ salts, such as Mg 2+ sulphate, are useful in reducing the pathophysiological consequences of preeclampsia with severe features and eclampsia. Although the mechanism of action of this Mg 2+ salt is not well understood, the available evidence suggests a beneficial effect of Mg 2+ for the mother and foetus. The mechanisms include a lower level of soluble fms-like tyrosine kinase 1 and endoglin, blockage of brain N-methyl-D-aspartate receptors, decreased inflammation mediators, activation of nitric oxide synthases, blockage of arginases, and reduced free radicals level. The maintenance of Mg 2+ homeostasis in pregnancy is crucial for an appropriate pregnancy progression. Oral Mg 2+ salts can be used for this purpose which could result in mitigating the deleterious consequences of this syndrome to the mother, foetus, and newborn., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Objective: To evaluate the osmotic fragility of red blood cells and the level of lipid peroxidation, the Ca(2+)-ATPase activity of red cell ghosts and placental homogenates from salt-loaded pregnant rats., Methods: Salt-loaded pregnant rats received 1.8% NaCl solution ad libitum as a beverage for seven days, starting on 15th day of pregnancy. Then, it was evaluated the level of lipid peroxidation and the Ca(2+)-ATPase activity of placental homogenates and red blood cell ghosts from control and experimental rats. Furthermore, the osmotic fragility of the red blood cells was evaluated by measuring the lysis of these cells when incubated with a NaCl solution with different osmolarities., Results: It was found that placental homogenates and red blood cell ghosts from experimental pregnant rats showed an increased level of lipid peroxidation and a lowered Ca(2+)-ATPase activity, as compared to control pregnant rats. They also presented an increased osmotic fragility of their red blood cells., Conclusions: Salt-loaded pregnant rats showed, similar to preeclamptic women, an increased level of lipid peroxidation and a lowered Ca(2+)-ATPase activity in placental and red blood cells membranes, as well as an increased osmotic fragility of the red blood cells.

Human sperm has several mechanisms to control its ionic milieu, such as the Na,K-ATPase (NKA), the Ca-ATPase of the plasma membrane (PMCA), the Na(+)/Ca(2) (+)-exchanger (NCX) and the Na(+)/H(+)-exchanger (NHE). On the other hand, the dynein-ATPase is the intracellular motor for sperm motility. In this work, we evaluated NKA, PMCA, NHE, NCX and dynein-ATPase activities in human sperm and investigated their correlation with sperm motility. Sperm motility was measured by Computer Assisted Semen Analysis. It was found that the NKA activity is inhibited by ouabain with two Ki (7.9 × 10(-9) and 9.8 × 10(-5) M), which is consistent with the presence of two isoforms of α subunit of the NKA in the sperm plasma membranes (α1 and α4), being α4 more sensitive to ouabain. The decrease in NKA activity is associated with a reduction in sperm motility. In addition, sperm motility was evaluated in the presence of known inhibitors of NHE, PMCA and NCX, such as amiloride, eosin, and KB-R7943, respectively, as well as in the presence of nigericin after incubation with ouabain. Amiloride, eosin and KB-R7943 significantly reduced sperm motility. Nigericin reversed the effect of ouabain and amiloride on sperm motility. Dynein-ATPase activity was inhibited by acidic pH and micromolar concentrations of Ca(2) (+). We explain our results in terms of inhibition of the dynein-ATPase in the presence of higher cytosolic H(+) and Ca(2) (+), and therefore inhibition of sperm motility., (© 2015 Society for Reproduction and Fertility.)

Objective: The aim of this study is to evaluate the effect of preeclampsia on the level of lipid peroxidation, activity and expression of both plasma membrane Ca(2+)- and Na(+), K(+)-ATPases in syncytiotrophoblast., Methods: The level of lipid peroxidation was estimated by measuring TBARS. ATPase activities were quantified by a colorimetric method measuring the amount of inorganic phosphate during the assay. Expression of Ca(2+)- and Na(+), K(+)-ATPases in syncytiotrophoblast plasma membranes and term placenta tissue sections was investigated using Western blot and immunohistochemistry, respectively., Results: Our results show a higher level of lipid peroxidation of syncytiotrophoblast plasma membranes from preeclamptic, as compared to uncomplicated pregnant women. Preeclampsia also significantly reduced the activity of Ca(2+)- and Na(+), K(+)-ATPases; however, expression of both ATPases was unaffected., Conclusion: Our findings suggest that the reduction of Ca(2+)- and Na(+), K(+)-ATPase activities during preeclampsia could be at least partially due to an increased level of lipid peroxidation of the syncytiotrophoblast plasma membranes.