Decline In ATPase Activity Research Articles

Comprehensive Assessment of Graphene Oxide Nanoparticles: Effects on Liver Enzymes and Cardiovascular System in Animal Models and Skeletal Muscle Cells.

The growing interest in graphene oxide (GO) for different biomedical applications requires thoroughly examining its safety. Therefore, there is an urgent need for reliable data on how GO nanoparticles affect healthy cells and organs. In the current work, we adopted a comprehensive approach to assess the influence of GO and its polyethylene glycol-modified form (GO-PEG) under near-infrared (NIR) exposure on several biological aspects. We evaluated the contractility of isolated frog hearts, the activity of two rat liver enzymes-mitochondrial ATPase and diamine oxidase (DAO), and the production of reactive oxygen species (ROS) in C2C12 skeletal muscle cells following direct exposure to GO nanoparticles. The aim was to study the influence of GO nanoparticles at multiple levels-organ; cellular; and subcellular-to provide a broader understanding of their effects. Our data demonstrated that GO and GO-PEG negatively affect heart contractility in frogs, inducing stronger arrhythmic contractions. They increased ROS production in C2C12 myoblasts, whose effects diminished after NIR irradiation. Both nanoparticles in the rat liver significantly stimulated DAO activity, with amplification of this effect after NIR irradiation. GO did not uncouple intact rat liver mitochondria but caused a concentration-dependent decline in ATPase activity in freeze/thaw mitochondria. This multifaceted investigation provides crucial insights into GOs potential for diverse implications in biological systems.

Chronic oral administration of beta-adrenoceptor agonist clenbuterol affects myosin heavy chain (MHC) expression in adult mouse heart

The aim of this study was to analyze the effects of chronic administration of the beta-adrenoceptor agonist clenbuterol (2 mg/kg body weight/day for a period of 30 days) on the major contractile protein (myosin) in the left ventricular muscle of the adult mouse heart. Separation of myosin heavy chain (MHC) isoforms on 7.5 % glycerol SDS-PAGE and subsequent quantification of the gels by laser densitometry showed a 6.5-fold increase in the beta-isoform of MHC in the clenbuterol-treated group. The alpha : beta ratio of these two isoforms in the control group was 98.16+/-0.14 %: 1.83+/-0.14 %, whereas in the treated group it was 88.05+/-1.15 % : 11.95+/-1.15 %. Actomyosin ATPase activity assay demonstrated a significant (20 %) decline in ATPase activity of the tissue in the beta-agonist-treated group. These results suggest that chronic clenbuterol treatment is capable to induced the transformation of MHC isoforms increasing the slow beta-MHC isoform, which may contribute to the altered contractile mechanics of clenbuterol-treated hearts.

HYPOCHLOROUS ACID INHIBITS CA2+-ATPASE ACTIVITY FROM SKELETAL MUSCLE SARCOPLASMIC RETICULUM 1286

Hypochlorous acid (HOCl) is produced by polymorphonuclear leukocytes that migrate and adhere to endothelial cells as part of the inflammatory process. HOCl is an extremely toxic oxidant that can react with a variety of cellular components. Concentrations have been reported as high as 200 uM in some tissues. Recent reports have indicated that myeloperoxidase, the enzyme that produces HOCl, is activated during and following submaximal bouts of exercise. In this study we show that HOCl inhibits SR Ca2+-ATPase activity. Following a 10 minute exposure, ATPase activity declined in a concentration dependent manner with an IC50 of 170 uM and complete inhibition by 3 mM. A reduction of ATP stimulated Ca2+ uptake into SR vesicles paralled the decline in ATPase activity. A concommitent reduction in free sulfhydryl groups (20.1 to 7.2 mol/mol protein) accompanied the HOCl induced inhibition of ATPase activity. HOCl also inhibited the FITC binding, indicating alterations in the structural integrity of the adenine nucleotide binding pocket. These findings suggest that the reactive oxygen specie, HOCl inhibits ATPase activity via a modification of endogenous SH groups supporting the contention that ROS disrupt normal Ca2+ handling in muscle cells.

Effect of Sodium Hypophosphite Feeding on Adenosine Triphosphatase Activity in Ageing <i>Zaprionus paravittiger</i> (Diptera)

Addition of antioxidant, sodium hypophosphite (SHP; 1 mM), to the diet of Zaprionus paravittiger (Diptera) results in depressed ATPase activity in both the sexes in comparison to the normal group. However, the rate of age-related decline in ATPase activity is lowered considerably in SHP fed group. Such changes in ATPase activity might be one of the important factors responsible for increased life span of flies with SHP feeding.

ATPase activity and force production in myofibrils and twitch characteristics in intact muscle from neonatal, adult, and senescent rat myocardium

To determine whether age-associated alterations in the cardiac muscle twitch could be related to altered myofibrillar ATPase activity or to an altered force-pCa relationship, these variables were measured in rat cardiac preparations across a broad age range. Between 2 and 6 months, maximum ATPase activity in detergent treated myofibrils decreased approximately two fold (0.166 +/- 0.01 v. 0.078 +/- 0.02 microM Pi/min X mg protein, P less than 0.001), but did not change with further aging (12 or 24 months). The Ca2+-dependent force in thin 'Triton skinned' papillary muscles was not age-related. ATPase activity and force exhibited identical Ca2+ sensitivity from the submicromolar to micromolar range: for ATPase activity pCa for 50% activity averaged 6.1 and Hill coefficients averaged 4.5; pCa for 50% force development was 6.1 and Hill coefficients of the force-pCa relation averaged 4.5; no age differences in these parameters were observed. In the intact muscles prior to skinning, neither twitch force nor the maximum rate of force production were age-related; however, indices of the time course of contraction, time to peak force, half relaxation time, and their sum, increased progressively, changing by approximately 30% from 2 to 24 months (P less than 0.001). Since the decline in ATPase activity occurred over the maturational period only, and did not change with further ageing, while the twitch duration changed progressively with age, it is concluded that the twitch prolongation of the senescent myocardium cannot be directly related to the age-related decline in myofibrillar ATPase activity.

Modulation of coupling factor ATPase activity in intact chloroplasts. Reversal of thiol modulation in the dark

Illumination of intact pea chloroplasts results in both the pH activation and the thiol modulation of the reversible protonmotive ATPase, or CF 0-CF 1 (Mills, J.D., Mitchell, P. and Schürmann, P. (1980) FEBS Lett. 112, 173–177). We have studied the reversal of the activation and thiol-modulation processes that occurs when illuminated chloroplasts are darkened. (1) Methyl viologen is shown to prevent light-dependent thiol modulation of CF 0-CF 1 in intact chloroplasts. Studies using methyl viologen indicate that the decline in ATPase activity of intact chloroplasts in the dark is due both to pH deactivation and thiol demodulation of CF 0-CF 1. Reillumination in the presence of methyl viologen reactivates CF 0-CF 1 complexes that have undergone pH deactivation, but does not allow thiol modulation to occur. (2) At 20°C, both pH deactivation and thiol demodulation of CF 0-CF 1 are complete within 10 min darkness. At 3.5°C, both processes are retarded, and require more than 30 min for completion. (3) Lysis of intact chloroplasts greatly retards the thiol demodulation of CF 0-CF 1. In the dark, addition of oxidants to lysed chloroplasts promotes thiol demodulation. Under these conditions, thioredoxin behaves as a weak oxidant, but glutathione has very little effect. Illumination of intact chloroplasts followed by rapid lysis and storage on ice stabilises the pH-activated, thiol-modulated state of CF 0-CF 1 for extended periods in the dark and increases the time required for thiol demodulation to well over 2 h. This method may prove to be useful for preparing thiol-modulated chloroplasts without the need to add or remove exogenous thiols. The results suggest that an oxidative system exists in the stroma which actively reverses thiol modulation of CF 0-CF 1 in the dark. Such a system would be expected if thiol modulation of CF 0-CF 1 were an important physiological process regulating reversible ATPase activity in vivo.

Elevated lymphocyte ATP-ase activity in patients with cancer of the uterine cervix.

Elevated lymphocyte Adenosine Tri-Phosphatase (ATP-ase) activity was found in 23 och 28 patients with cervical uterine carcinomas of various stages. Treatment with external irradiation and radium insertion was followed by a decline in the lymphocyte ATP-ase activity in 22 patients, while the activity remained unchanged in one patient. No correlation between the tumour stage and the lymphocyte ATP-ase activity was demonstrated. In 24 patients the clinical effect of the treatment was well correlated with the decline in ATP-ase activity. It is suggested that the determination of lymphocyte ATP-ase activity could be valuable in screening for cervical carcinoma and for follow-up after radical treatment.

ATP-ase activity of lymphocytes from patients with carcinomas of the urinary bladder.

In 13 out of 26 patients with urinary bladder carcinomas in various stages of malignancy, the ATP-ase activity of circulating lymphocytes was found significantly elevated. A decline in the ATP-ase activity was demonstrated in 14 of 17 patients re-investigated after treatment, while the activity remained unchanged in 2 and rose in 1 patient. No correlation between the clinical tumour stage and the lymphocyte ATP-ase activity was found, but the activity was closely correlated to the histological grade of malignancy. In 11 of the 17 patients the clinical effect of the treatment was closely correlated to a decline in ATP-ase activity. Determination of lymphocyte ATP-ase activity is suggested as an additional and simple help in the diagnosis of bladder carcinoma and in the follow-up control after treatment of patients with this disease.

Temperature and aging effects on the fluorescence intensity of myosin-ANS complex

Previous work indicated that certain conditions favoring moderate interaction of myosin with the fluorescent dye, ANS, corresponded to conditions favorable for ATP-ase activity of myosin, but conditions leading to extensive dye-binding corresponded to loss of enzymic activity. The present study indicates that two additional conditions resulting in a progressive decline in ATPase activity are also accompanied by a progressive increase in dye-binding: slow aging at 4 ° and brief exposure to temperatures from 25 to 50 °. The results are interpreted as reflecting a conformational change in the protein which reduces the effectiveness of myosin as an enzyme and exposes nonpolar groups conductive to ANS binding.