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Bicyclophosphates are potent chloride channel blockers
110
P125
Cell Biology lnternationd
MEMBRANE POTENTIAL CHANGES IN A PLANT CELL INDUCED BY LOWINTENSITY MM-MICROWAVE
I.YLJ. Petriv, Institute of Radioengineering and Electronics Academy of the Sciences of the USSR, Lab.169, Prospect Marxa 18, Moscow, USSR It is found that the initial direction of the changes of membrane potential (Aw) in a plant cells induced by mmmicrowave (7.1 mm) radiation of low (10 mW/sq.cm) intensity (MWR) is opposite to that of the changes Aw caused by temperature elevation by a magnitude equivalent to the heating of cells due to MWR absorption. When a cell is irradiated with MWR of high intensity the next phase of changes Aw is observed which is due to temperature raising in the cells caused by MWR radiation absorption. It has been shown that the MWR effect is not probably associated with either absolute cell temperature rising due to MWR absorption or the initial velocity of the temperature rise under MWR irradiation of cells and is probably due to “nonthetmal” effect of the MWR on conformation of the protein portion of the ATP-synthetase complex leading to activation of the latter.
BICYCLCFWSPHATESAIlR POTENT CDIQRIDE CDMIIEL BuIcI(EBs V.Lubimov, V.Bormotov. Institute A.Redkozubov, Active Substances USSR of Physiologically Academy of Sciences, Chernogolovka,142432, USSR. Using patch-clamp and intracellular potential measurement the action 4-alkyl-bicyclophosphatea (BCP) on chloride channels in membrane of identified neurones of qollusc Limaea Stagnalis One of the 4-ethyl-SCP in was investigated. concentrations 0,05-0,5 pM reversibly induces the change of neurone resting potential from -40 mV to about -70 nV. The effect of 4-ethyl-RCP on voltage-dependent chloride channels in patches At concentrations in depends on concentration. in the range of 0,5-0,05 pM BCP results instantaneous decreasing open time of channels to 30 times, at the concentrations a bit less than 0,05 pM BCP induces the degradation of conductance to smaller sublevels until full disappearing of current through the Cl-channel. The blocking effect of BCP is voltage-dependent. These data suggest that the BCP are a new potent blocker of chloride channels.
PI27
P126
Reports, Vol. 14, Abstracts Supplement
1990
A Na+TRANSPORT PATHWAY IN PIG LENS
MEMBRANES. Alberti Giovanna, Gandolfi A. Stefano, Maraini Gio_ vanni; Istituto di Oftalmologia Universiti di Parma, Parma, Italy Protein preparations extracted by 10 mM CHAPS from membrane enriched fractions obtained from the lens epithelium and outer cortex of lyear old pigs, were incorporated in phosphatidilcholine vesicles. 22Na influx experiments were then performed according to the technique described by Garty and al. (J. Biol. Chem.,W3) ). was slow The time course of the 22Na influx The presence of 50 mM Na+ out (t2= 20-25 min.). almost completely inhibited the uptake of radiolabelled sodium while equivalent concentrations of K+, Li+, and choline did not exert any appreciable effect on 22Na movement. Kinetic analysis was performed by measuring the 22Na influx at increasing concentrations of Na+ out ( V/S ). The experimental points were solved by a single-component Miche lis-Menten equation with Km values ranging from 2 to 9 mh! (4 indipendent experiments). Amiloride seems to exert a 50% inhibition on the being anyway negligiinflux of 22Na, the effect ble at concentrations lower than 0.5 mM. These data are then consistent with the existence of a Na+ specific transport pathway in pig lens membranes.
ROLE OF SOME ARACHIDONIC ACID METABOLITES ON HYPOTONIC SHOCK ACTIVATED CHLORIDE TRANSPORT IN HUMAN FIBROBLASTS. Teresa Mastrocola and Michela Rugolo,Dip.di Biologia Univ.di Bologna,Via Irnerio 42, Bologna,Italy. The loss of KC1 observed in human fibroblasts during regulatory volume decrease (RVDI,involves the activation of separate conductive pathways for Cl- and K+ transport.It has been recently proposed that arachidonic acid metabolites might be involved. The cyclooxygenase pathway leading to prostaglandins synthesis is inhibited by indomethacin,whereas the lipooxygenase pathway,leading to leukotrienes production,is blocked by nordihydroguaiaretic acid (NDGAI. The addition of indomethacin was without effect on the activation of SBcl- efflux induced by hypotonic medium. The finding that both PGEl and PGE2 failed to activate Cl- efflux in isotonic medium seems to indicate that prostaglandins do not play any role in RVD in fibroblasts. Conversely,the addition of NDGA almost completely inhibited the stimulation of Cl- efflux induced by hypotonic shock, suggesting that RVD is likely to be mediated via stimulation of leukotrienes synthesis. Studies are in progress to determine the production of PGE2 and leukotrienes in human fibroblasts exposed to isotonic and hypotonic media.
P126
P125
Cell Biology lnternationd
MEMBRANE POTENTIAL CHANGES IN A PLANT CELL INDUCED BY LOWINTENSITY MM-MICROWAVE
I.YLJ. Petriv, Institute of Radioengineering and Electronics Academy of the Sciences of the USSR, Lab.169, Prospect Marxa 18, Moscow, USSR It is found that the initial direction of the changes of membrane potential (Aw) in a plant cells induced by mmmicrowave (7.1 mm) radiation of low (10 mW/sq.cm) intensity (MWR) is opposite to that of the changes Aw caused by temperature elevation by a magnitude equivalent to the heating of cells due to MWR absorption. When a cell is irradiated with MWR of high intensity the next phase of changes Aw is observed which is due to temperature raising in the cells caused by MWR radiation absorption. It has been shown that the MWR effect is not probably associated with either absolute cell temperature rising due to MWR absorption or the initial velocity of the temperature rise under MWR irradiation of cells and is probably due to “nonthetmal” effect of the MWR on conformation of the protein portion of the ATP-synthetase complex leading to activation of the latter.
BICYCLCFWSPHATESAIlR POTENT CDIQRIDE CDMIIEL BuIcI(EBs V.Lubimov, V.Bormotov. Institute A.Redkozubov, Active Substances USSR of Physiologically Academy of Sciences, Chernogolovka,142432, USSR. Using patch-clamp and intracellular potential measurement the action 4-alkyl-bicyclophosphatea (BCP) on chloride channels in membrane of identified neurones of qollusc Limaea Stagnalis One of the 4-ethyl-SCP in was investigated. concentrations 0,05-0,5 pM reversibly induces the change of neurone resting potential from -40 mV to about -70 nV. The effect of 4-ethyl-RCP on voltage-dependent chloride channels in patches At concentrations in depends on concentration. in the range of 0,5-0,05 pM BCP results instantaneous decreasing open time of channels to 30 times, at the concentrations a bit less than 0,05 pM BCP induces the degradation of conductance to smaller sublevels until full disappearing of current through the Cl-channel. The blocking effect of BCP is voltage-dependent. These data suggest that the BCP are a new potent blocker of chloride channels.
PI27
P126
Reports, Vol. 14, Abstracts Supplement
1990
A Na+TRANSPORT PATHWAY IN PIG LENS
MEMBRANES. Alberti Giovanna, Gandolfi A. Stefano, Maraini Gio_ vanni; Istituto di Oftalmologia Universiti di Parma, Parma, Italy Protein preparations extracted by 10 mM CHAPS from membrane enriched fractions obtained from the lens epithelium and outer cortex of lyear old pigs, were incorporated in phosphatidilcholine vesicles. 22Na influx experiments were then performed according to the technique described by Garty and al. (J. Biol. Chem.,W3) ). was slow The time course of the 22Na influx The presence of 50 mM Na+ out (t2= 20-25 min.). almost completely inhibited the uptake of radiolabelled sodium while equivalent concentrations of K+, Li+, and choline did not exert any appreciable effect on 22Na movement. Kinetic analysis was performed by measuring the 22Na influx at increasing concentrations of Na+ out ( V/S ). The experimental points were solved by a single-component Miche lis-Menten equation with Km values ranging from 2 to 9 mh! (4 indipendent experiments). Amiloride seems to exert a 50% inhibition on the being anyway negligiinflux of 22Na, the effect ble at concentrations lower than 0.5 mM. These data are then consistent with the existence of a Na+ specific transport pathway in pig lens membranes.
ROLE OF SOME ARACHIDONIC ACID METABOLITES ON HYPOTONIC SHOCK ACTIVATED CHLORIDE TRANSPORT IN HUMAN FIBROBLASTS. Teresa Mastrocola and Michela Rugolo,Dip.di Biologia Univ.di Bologna,Via Irnerio 42, Bologna,Italy. The loss of KC1 observed in human fibroblasts during regulatory volume decrease (RVDI,involves the activation of separate conductive pathways for Cl- and K+ transport.It has been recently proposed that arachidonic acid metabolites might be involved. The cyclooxygenase pathway leading to prostaglandins synthesis is inhibited by indomethacin,whereas the lipooxygenase pathway,leading to leukotrienes production,is blocked by nordihydroguaiaretic acid (NDGAI. The addition of indomethacin was without effect on the activation of SBcl- efflux induced by hypotonic medium. The finding that both PGEl and PGE2 failed to activate Cl- efflux in isotonic medium seems to indicate that prostaglandins do not play any role in RVD in fibroblasts. Conversely,the addition of NDGA almost completely inhibited the stimulation of Cl- efflux induced by hypotonic shock, suggesting that RVD is likely to be mediated via stimulation of leukotrienes synthesis. Studies are in progress to determine the production of PGE2 and leukotrienes in human fibroblasts exposed to isotonic and hypotonic media.
P126