Time course of metabolism of aldrin and dieldrin by suspension cultures

Time course, up to 100d, of uptake and metabolism of aldrin and dieldrin added at subculture to suspension cultures from Phaseolus vulgaris (French bean) root and shoot, and Solanum tuberosum (potato) tuber comparable, with rapid dieldrin production and delayed appearance of other metabolites. When aldrin and dieldrin not added to Phaseolus cultures until 10 or 20d after subculture usual extent of conversion of aldrin to dieldrin, but reduced production of other metabolites, and growth inhibition negated. Increasing volumes of 2-methoxyethanol had detrimental effect on growth and uptake and metabolism. Dieldrin production maximal during rapid growth phase and probably independent of other conversions.     

Inhibition of ATPases by gymnemic acid

A specially prepared and partially fractionated preparation of gymnemic acid compounds were found to be inhibitory to the ATPase system from housefly brain and labellum, and fish brain. Enzyme activity in a homogenate fraction from labellum showed greatest sensitivity to the gymnemic acid preparation. Na⁺-K⁺ ATPase activity from the labellum, which contains the sweet taste sensory receptors, was inhibited by over 92% at a concentration of 4 middot; 10^?6M gymnemic acid. Because gymnemic acid compounds are specific suppressants of sweet receptors, the evidence presented in this paper implies that a portion of the ATPase system may be biochemically important in the sweet-sensing mechanism.     

Inhibition of ion transport ATPases by HNE

4-Hydroxy-2,3-trans-nonenal (HNE), a major lipid peroxidation product, has been shown to react with specific amino acid residues of proteins and alter their function. In vitro exposure of erythrocyte ghosts and neutrophil membranes to HNE results in the inhibition of ion transport ATPases. Neutrophil membrane Ca2+-ATPase is strongly inhibited by micromolar concentrations of HNE, while HNE is considerably less effective against neutrophil Mg2+-ATPase and the erythrocyte ghost enzymes.     

Consistency of metabolism of aldrin and dieldrin in suspension cultures from Phaseolus vulgaris root

Reproducibility of metabolism of aldrin and dieldrin in cell suspension cultures from Phaseolus vulgaris (French Bean) root, and effects of variations in hormonal supplementation and light, studied. Aldrin always converted to dieldrin, aldrin-transdihydrodiol, and other unidentified more polar metabolites, but not to dihydrochlordene-dicarboxylic acid. Dieldrin always converted to photodieldrin and more polar metabolites, but not to aldrin-transdihydrodiol. Metabolism reasonably consistent from one subculture to next, basically unaffected by alterations in medium tested, or by presence or absence of light. Variations observed quantitative rather than qualitative supporting validity of use of tissue culture in metabolic studies on xenobiotics. Photodieldrin shown to be a direct product of dieldrin metabolism and not the result of microbial or environmental interference.     

Inhibition of Mg2+ and Na(+)-K+ ATPases in selected tissues of fish, Cyprinus carpio under fenvalerate toxicity.

The changes in the magnesium adenosine triphosphatase (Mg2+ ATPase) and sodium-potassium adenosine triphosphatase (Na(+)-K+ ATPase) in gill, brain, liver and muscle tissues of freshwater fish, Cyprinus carpio at 6, 12, 24 and 48 hr exposure periods were studied after subjecting to sublethal concentration (10 micrograms/lit) of fenvalerate. Mg2+ ATPase and Na(+)-K+ ATPase activities were inhibited in all the tissues of fenvalerate exposed fish. The per cent inhibition increased with increase in the period of exposure and the possible reasons for the inhibition patterns are discussed.     

Inhibition of spider mite ATPases by plictran and three organochlorine acaricides

The ATPase enzyme system from two-spotted spider mites, $\text{Tetranychus}$$\text{urticae}$ (Koch) was sensitive, in vitro, to four acaricides. Tricyclohexylhydroxytin (Plictran^R) was an outstanding inhibitor of oligomycin-sensitive (mitochondrial) Mg²⁺ATPase from fish brain and spider mite homogenates. The I₅₀ values were 6.6×10^?11M and 6.2×10^?10M, respectively. Less effective were chlorbenside, chlorfenethol and ovotran. Plictran at a higher concentration (2×10^?7M) was also more effective on Na⁺-K⁺ATPase both in mites and fish brain homogenates as compared to chlorfenethol, chlorbenside and ovotran. Plictran inhibited oligomycin-insensitive Mg²⁺ATPase at concentrations of 10^?8M but stimulated at high concentrations (5×10^?6M and higher).     

Effects of plant lectins on cation-activated brain ATPases.

The effects of concanavalin A (con A) and wheat germ agglutinin (WGA) on cation-activated ATPases in a crude homogenate of rat brain corpus striatum were examined. Con A enhanced the activity of Mg⁺⁺-dependent-, and Ca⁺⁺-activated-ATPases, and inhibited (Na⁺ + K⁺)- ATPase activity. WGA enhanced Mg⁺⁺-dependent ATPase activity, but did not alter the activity of the other two components. The specificity of these interactions was demonstrated by reversal with specific lectin-interacting sugars. The possibility that these effects may be mediated by lectin-binding to physiologic regulatory sites, as well as the possible role of these interactions in the etiopathology of schizophrenia are discussed.     

Inhibition of Na,K-ATPase from chick brain by polyamines.

The amounts of the polyamines putrescine, spermine and spermidine as well as the Na,K-ATPase activity have been determined in the developing chick brain. The amounts of spermine and spermidine per gram fresh weight do not change significantly, the amount of putrescine declines until the 17th day of incubation after which an increase takes place. Spermine is able to inhibit the Na,K-ATPase from chick brain competitively. Half maximal inhibition is achieved at 4 X 10(-5) mol/1 spermine. This polyamine functions as an allosteric inhibitor; the Hill coefficient is 2.2 +/- 0.3. A regulatory effect of spermine on the Na,K-ATPase from chick brain is discussed. In contrast to spermine 1 mmol/1 spermidine inhibits the Na,K-ATPase only slightly, while 1 mmol/1 putrescine does not inhibit the Na,K-ATPase at all.     

Inhibition of proton-translocating ATPases of Streptococcus mutans and Lactobacillus casei by fluoride and aluminum

One of the major effects of fluoride on oral bacteria is a reduction in acid tolerance, and presumably also in cariogenicity. The reduction appears to involve transport of protons across the cell membrane by the weak acid HF to dissipate the pH gradient, and also direct inhibition of the F₁F₀, proton-translocating ATPases of the organisms, especially for Streptococcus mutans. This direct inhibition by fluoride was found to be dependent on aluminum. The dependence on aluminum was indicated by the protection against fluoride inhibition afforded by the Al-chelator deferoxamine and by loss of protection after addition of umolar levels of Al³⁺, which were not inhibitory for the enzyme in the absence of fluoride. The F₁ form of the enzyme dissociated from the cell membrane previously had been found to be resistant to fluoride in comparison with the F₁F₀ membrane-associated form. However, this difference appeared to depend on less aluminum in the F₁ preparation in that the sensitivity of the F₁ enzyme to fluoride could be increased by addition of umolar levels of Al³⁺. The effects of Al on fluoride inhibition were apparent when enzyme activity was assayed in terms of phosphate release from ATP or with an ATP-regenerating system containing phosphoenolpyruvate, pyruvate kinase, NADH and lactic dehydrogenase. Also, Be²⁺ but not other metal cations, e.g. Co²⁺, Fe²⁺, Fe³⁺, Mn², Sn²⁺, and Zn²⁺, served to sensitize the enzyme to fluoride inhibition. The differences in sensitivities of enzymes isolated from various oral bacteria found previously appeared also to be related to differences in levels of Al. Even the fluoride-resistant enzyme of isolated membranes of Lactobacillus casei ATCC 4646 could be rendered fluoride-sensitive through addition of Al³⁺. Thus, the F₁F₀ ATPases of oral bacteria were similar to E₁E₂ ATPases of eukaryotes in being inhibited by Al-F complexes, and the inhibition presumably involved formation of ADP-Al-F _inf3 ^sup- complexes during catalysis at the active sites of the enzymes.     

Inhibition of microsomal ATPases by high concentration of Mg2+ in tracheal epithelial cells.

Previous work in our laboratory established the presence of two types of microsomal ATPases, a low-affinity vanadate-sensitive (LAVS) and a high-affinity vanadate-sensitive (HAVS) ATPases, in tracheal epithelial cells. These ATPases were identified as Ca2+-ATPases by specific inhibitors and microsomal Ca2+ uptakes. Since the regulatory roles of Mg2+ on both cellular Ca2+-signaling and epithelial transports were demonstrated, the effects of Mg2+ on these ATPases were investigated. Mg2+-dependence of ATPase activity appeared bell-shaped with a maximal activity at 1-2 mM Mg2+ and Mg2+ at higher than 2 mM inhibited these enzymes. In a kinetic analysis of the LAVS ATPase inhibition, high concentration of Mg2+ appeared to inhibit the binding of ATP to a substrate-binding site. The microsomal 45Ca2+ uptakes mediated by both ATPases were also inhibited by high concentration of Mg2+. In order to test whether high concentration of Mg2+ directly inhibits these enzymes, microsomes were made leaky by the treatment of Triton X-100 and the microsomal ATPases were solubilized with CHAPS. The leaky microsomal ATPases and CHAPS-solubilized ATPases were similarly inhibited by high concentration of Mg2+, suggesting that Mg2+ directly inhibit these enzymes. In conclusion, Mg2+ has two types of modulatory effects on these enzymes, a catalytic effect at low concentration and an inhibitory effect at high concentration.     

Epoxidation of aldrin to exo-dieldrin by soil bacteria.

Twenty-two strains of soil bacteria, including representatives of the genera Bacillus, Micromonospora, Mycobacterium, Nocardia, Streptomyces, Thermoactinomyces, and Pseudomonas and 10 unidentified gram-negative, motile, rod-shaped bacteria, were shown to degrade aldrin to its epoxide dieldrin. In every case, the exo-stereoisomer of dieldrin was produced exclusively.     

Specific Inhibition of Cell Wall-Bound ATPases by Fungal Suppressor from Mycosphaerella pinodes

Activities of phosphatases were found in the fractions whichwere solubilized from cell walls of both pea and cowpea seedlingswith 0.5 M NaCl. These phosphatases hydrolyzed triphosphonucleotidesin the order: UTP=CTP>GTP>ATP; and UTP=GTP>CTP=ATP,respectively. The activities of a pyrophosphatase and a p-nitrophenylphosphatasewere also detected in these fractions. The suppressor in thespore germination fluid of a pea pathogen,Mycosphaerella pinodes,inhibited all of these phosphatase activities in the fractionsolubilized from pea cell walls, but it rather enhanced onlythe activity of the ATPase among those phosphatases from thecowpea cell wall. Hydrolysis of ATP by a cell wall fractionof pea was also markedly inhibited by the suppressor, whilehydrolysis of ATP by similar fractions from cowpea, kidney beanand soybean were rather enhanced by the suppressor, as wellas by the elicitor. Thus, the cell wall-bound ATPases respondedto the suppressor species-specifically. These cell wall-boundATPases seemed to be different from the plasma membrane ATPasesin several respects. The results suggest that plants recognizethe fungal signals not only on their plasma membranes but alsoon their cell walls and, moreover that putative receptors forthe fungal signals might be located close to cell wall-boundATPases or might even be these ATPases themselves. (Received November 16, 1994; Accepted April 20, 1995)     

Inhibition of glucose transport into brain by phlorizin, phloretin and glucose analogues.

An indicator dilution technique with 22Na+ as the intravascular marker was used to measure unidirectional transport of D-[6-3H]glucose from blood into the isolated, perfused dog brain. 18 compounds which are structurally related to glucose were tested for their ability to inhibit glucose transport. The data suggest that no single hydroxyl group is absolutely required for glucose transport, but rather that glucose binding to the carrier probably occurs through hydrogen bonding at several sites (hydroxyls on carbons 1, 3, 4 and 6). In addition, alpha-D-glucose has higher affinity for the carrier than does beta-D-glucose. A separate series of experiments demonstrated that phlorizin and phloretin are competitive inhibitors of glucose transport into brain; however, phloretin is partially competitive and inhibits at lower concentrations than does phlorizin. Inhibition by phlorizin and phloretin is mutually competitive, indicating that these compounds compete for binding to the glucose carrier. Comparison with the results reported in the literature for similar studies using the human erythrocyte demonstrates a fundamental similarity between glucose transport systems in the blood-brain barrier and erythrocyte.