Characteristics of non-specific permeability and H + -ATPase inhibition induced in the plasma membrane of Nitella flexilis by excessive Cu 2+

Abstract

Effects of Cu2+ on a non-specific conductance and H+-ATPase activity in the plasma membrane of the freshwater alga Nitella flexilis L. Agardh was studied using a conventional microelectrode voltage-clamp technique. We show that a Cu2+-induced increase in the non-specific conductance is related to the formation of pores in the plasma membrane. Pore formation is the result of unidentified chemical reactions, since the Q10 for the rate of increase of conductance over time was about 3. Various oxidants and antioxidants (10 mmol/l H2O2, 10 mmol/l ascorbate, 100 microg/ml superoxide dismutase, and 100 microg/ml catalase) did not alter Cu2+-induced changes in the plasma membrane conductance, suggesting that the effect of Cu2+ was unrelated to peroxidation of plasma-membrane lipids. In contrast, organic and inorganic Ca2+-channel antagonists (nifedipine, Zn2+, Cd2+, Fe2+, Ni2+) inhibited the Cu2+-induced non-specific conductance increase. This suggests that changes in Ca2+ influx underlie this effect of Cu2+. Decreasing the pH or the ionic strength of external solutions also inhibited the Cu2+-induced plasma-membrane conductance increase. Copper was also found to inhibit plasma-membrane H+-ATPase activity with half-maximal inhibition occurring at about 5-20 micromol/l and full inhibition at about 100-300 micromol/l. The Hill coefficient of Cu2+ inhibition of the H+-ATPase was close to two.

Different effect of cadmium and copper on H+-ATPase activity in plasma membrane vesicles from Cucumis sativus roots

“…The plant plasma membrane (PM) can be regarded as the first structure that is a target for heavy-metal toxicity. An increase in permeability related to membrane damage is observed in plants that have been subjected to heavy-metal stress (De Vos et al , 1991, 1992; Demidchik et al , 1997, 2001; Murphy and Taiz, 1997; Murphy et al , 1999). One of the physiological responses to excess Cu is K + efflux from the roots.…”

The effect of aluminium on bioelectrical activity of the Nitellopsis obtusa cell membrane after H+-ATPase inhibition

“…Small changes in pump activity are thought to be important for many aspects of plant growth and development. For example, many studies have found changes in pump activity in response to a variety of environmental conditions, including salt stress, hormones, light, and pathogens [5,6]. The regulation of H + -ATPase activity not only allows nutrient uptake in plant cells but also controls water fluxes in stomatal guard cells and to pulvinar motor cells [7].…”

The effect of vitamin C on morphine self-administration in rats

“…[615] It has been reported that an increase in the activity of Na, K + ATPase is partly responsible for the two major opiate effects in the brain, which create hyper polarization in the membrane and also inhibition of neurotransmitter release. [14] The AA dose dependently decreases the analgesic effect of morphine in mice,[19] and it may reduce the analgesic effect of morphine in patients. These results, along with others’ knowledge, show that AA modulates the synaptic action of dopamine and glutamate, which suggests that even very high doses of AA, which are known to be non-toxic, may be used with dopaminergic antagonist drugs, to treat the morphine-abstinence syndrome.…”

“…[1112] Both the glutamatergic and dopaminergic systems are involved in the dependence and tolerance of morphine and morphine withdrawal syndrome signs,[13] and all these treatments are majorly affected by AA. [1415] From the previous studies it is not clear as to what dose of AA can prevent tolerance to opioids (especially morphine). Therefore, in this investigation we endeavor to determine the effect of low and high doses of AA on self-administration of morphine as well as on morphine withdrawal symptoms, in rats.…”