Probing an open CFTR pore with organic anion blockers.

The cystic fibrosis transmembrane conductance regulator (CFTR) is an ion channel that conducts Cl- current. We explored the CFTR pore by studying voltage-dependent blockade of the channel by two organic anions: glibenclamide and isethionate. To simplify the kinetic analysis, a CFTR mutant, K1250A-CFTR, was used because this mutant channel, once opened, can remain open for minutes. Dose-response relationships of both blockers follow a simple Michaelis-Menten function with K(d) values that differ by three orders of magnitude. Glibenclamide blocks CFTR from the intracellular side of the membrane with slow kinetics. Both the on and off rates of glibenclamide block are voltage dependent. Removing external Cl- increases affinity of glibenclamide due to a decrease of the off rate and an increase of the on rate, suggesting the presence of a Cl- binding site external to the glibenclamide binding site. Isethionate blocks the channel from the cytoplasmic side with fast kinetics, but has no measurable effect when applied extracellularly. Increasing the internal Cl- concentration reduces isethionate block without affecting its voltage dependence, suggesting that Cl- and isethionate compete for a binding site in the pore. The voltage dependence and external Cl- concentration dependence of isethionate block are nearly identical to those of glibenclamide block, suggesting that these two blockers may bind to a common binding site, an idea further supported by kinetic studies of blocking with glibenclamide/isethionate mixtures. By comparing the physical and chemical natures of these two blockers, we propose that CFTR channel has an asymmetric pore with a wide internal entrance and a deeply embedded blocker binding site where local charges as well as hydrophobic components determine the affinity of the blockers.

Cytoprotective effect of taurine against hypochlorous acid toxicity to PC12 cells.

Taurine has been shown to be an effective scavenger of hypochlorous acid (HOCl). The role of HOCl is well established in tissue damage associated with reperfusion injury mediated by neutrophils. The role of HOCl in CNS injury and inflammatory reactions has not been well established. Myeloperoxidase activity is present in the CNS and it has been associated with ischemic injury. The aim of the present study was to determine the cytotoxicity of HOCl in a neuronal cell line (PC12) and the ability of taurine to prevent or reverse neurotoxicity. PC12 cells were grown in 96 well plates at a plating density of approximately 100,000 cells per well. HOCl was made up fresh from NaOCl for each experiment and the concentration verified spectrophotometrically. PC12 cells were exposed to HOCl for 1 hour in phosphate-buffered saline. Taurine was added at the time of HOCl treatment and in some experiments a post-treatment with taurine was performed by adding 1 or 10 mM taurine to the culture media (RPMI 1640). The cells were allowed 24 hours to recover and viability was determined using a tetrazolium-based (MTT) assay. The first series of experiments evaluated the toxicity of HOCl and the efficacy of taurine to protect PC12 cells. HOCl at 50 microM reduced PC12 cell viability by 50% and 150 microM reduced viability to <25% of control levels. Taurine (0.5-20 mM) was tested for cytoprotection against 150 microM HOCl and PC12 cells treated with 0.5 mM taurine exhibited only a 20% reduction in viability compared to untreated controls. Taurine concentrations of 1 mM or higher provided nearly 100% protection against HOCl. A second study was performed comparing taurine to beta-alanine, glutathione and isethionic acid. HOCl (100 microM) reduced viability to 25 +/- 1% of controls and taurine, beta-alanine and glutathione at 1 mM provided nearly complete protection. In contrast, isethionic acid, which lacks an amino group, failed to provide protection. Taurine (1 or 10 mM) added after 50 microM HOCl treatment did not provide any protection and PC12 cell viability was reduced to <39% of controls. In contrast, if taurine (50 microM) was present during the HOCl treatment and 1 mM taurine was added after the treatment, PC12 cell viability was 80 +/- 5% of controls. A combination of 250 microM taurine during the HOCl treatment and 1 mM taurine post-treatment produced 100% protection. These results clearly show that taurine is an efficient scavenger of HOCl and can prevent neuronal damage caused by HOCl. Since myeloperoxidase expression in the CNS is increased by ischemia, one function of taurine released during an ischemic event may be to scavenge HOCl and provide neuroprotection.

Differential regulation of Na+ and Cl- conductances by PTX-sensitive G proteins in fetal lung apical membrane vesicles.

In apical membrane vesicles (AMV) prepared from late gestation fetal guinea pig lung we show that conductive 22Na+ uptake is modulated by at least two pathways involving pertussis toxin (PTX)-sensitive G proteins. Intravesicular incorporation of 100 microM GTPgammaS into vesicles resuspended in NaCl caused a significant stimulation (P<0. 05) of conductive Na+ uptake in AMV to 150+/-10% (n=10) of control, whereas GDPbetaS reduced uptake to 65+/-9% (n=4) of control. This contrasting response to GTPgammaS and GDPbetaS is characteristic of a G protein mediated pathway. GTPgammaS induced a significantly smaller stimulation, 125+/-8% (n=5) of control, in the presence of the relatively impermeant anion isethionate (Ise-). Taken together, these data indicate modulation of both Na+ and Cl- channels in the apical membrane by co-localised G protein(s). Treatment with PTX stimulated conductive 22Na+ uptake to 171+/-20% (n=13) of control in AMV resuspended in NaCl, but did not have a significant effect, 94+/-19% of control, in the presence of NaIse indicating the existence of tonic activation of Cl- channels in these AMV under resting conditions. As the combined effects of PTX and GTPgammaS diminished uptake, we propose that the G protein(s) responsible for Na+ channel activation in response to GTPgammaS is PTX-sensitive and that additional PTX-insensitive G proteins might also modulate 22Na+ uptake in these AMV. The presence of Gialpha1, Gialpha2, Gialpha3 and Goalpha in this apical membrane preparation was confirmed by PTX catalysed [32P]ADP-dependent ribosylation and Western blotting. Incubation of AMV with 200 microM DTT caused an inhibition of conductive Na+ uptake in AMV resuspended in NaCl or NaIse to 66+/-8% (n=11) and 64+/-8% (n=6) of control respectively. Pre-treatment with DTT did not affect the ability of GTPgammaS to stimulate conductive Na+ uptake suggesting that the regulation of 22Na+ uptake in late gestation guinea pig fetal lung AMV is unlikely to involve an associated regulatory protein.

Ion currents and mechanisms of modulation in the radula opener muscles of Aplysia.

Ion currents and mechanisms of modulation in the radula opener muscles of Aplysia. J. Neurophysiol. 78: 2372-2387, 1997. Numerous studies of plasticity in the feeding behavior of Aplysia have shown that substantial plasticity is due to peripheral neuromodulation of the feeding musculature. Extensive previous work focusing on the accessory radula closer (ARC) muscle has led to the realization that a major function of the modulation in that muscle may be to ensure efficient coordination between its contractions and those of its antagonist muscles. For a more complete understanding, therefore, we must study these muscles also. Here we have studied the radula opener muscles I7-I10. Using single isolated muscle fibers under voltage clamp, we have characterized ion currents gated by voltage and by the physiological contraction-inducing neurotransmitter acetylcholine (ACh) and the effects of the physiological modulators serotonin, myomodulins A and B, and FMRFamide. Our results explain significant aspects of the electrophysiological behavior of the whole opener muscles, as well as why the opener and ARC muscles behave similarly in many ways yet differently in some key respects. Opener muscles express four types of K currents: inward rectifier, A-type [IK(A)], delayed rectifier [IK(V)], and Ca2+-activated [IK(Ca)]. They also express an L-type Ca current [ICa] and a leakage current. ACh activates a positive-reversing cationic current [IACh(cat)] and a negative-reversing Cl current [IACh(Cl)]. The opener muscles differ from the ARC in that, in the openers, activation of IK(A) occurs approximately 9 mV more positive and there is much less IACh(Cl). In both muscles, IACh(cat) most likely serves to depolarize the muscle until ICa activates to supply Ca2+ for contraction, but further depolarization and spiking is opposed by coactivation of IK(A), IK(V), IK(Ca), and IACh(Cl). Thus the differences in IK(A) and IACh(Cl) may well be key factors that prevent spikes in the ARC but often allow them in the opener muscles. As in the ARC, the modulators enhance ICa and so potentiate contractions. They also activate a modulator-specific K current, which causes hyperpolarization and depression of contractions. Finally, in the opener muscles but not in the ARC, the modulators activate a depolarizing cationic current that may help phase-advance the contractions. Each modulator exerts these effects to different degrees and thus has a distinct effect on voltage and contraction size and shape. The overall effect then will depend on the specific combinations of modulators released in different behaviors. By understanding the modulation in the opener muscles, as well as in the ARC, we are now in a position to understand how the behavior of the two muscles is coordinated under a variety of circumstances.

Role of membrane-permeable ions in renin secretion by renal juxtaglomerular cells.

In this study we examine the role of membrane-permeable ions in renin secretion from renal juxtaglomerular (JG) cells. To this end, extracellular Cl- (100 mmol/l) in the culture medium of isolated mouse renal JG cells was replaced by the permeable anion NO3- or by the membrane-impermeable anion isethionate. Alternatively, extracellular Na+ (100 mmol/l) was substituted by the membrane-impermeable cation choline. The effects of these ion substitutions on basal and stimulated renin secretion were then examined. Renin secretion was stimulated by the adenylate cyclase activator forskolin (10 microM), the NO donor sodium nitroprusside (SNP, 100 microM), the calmodulin antagonist calmidazolium (10 microM), by lowering extracellular Ca2+ concentration ([Ca2+]e) with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) (2 mM), and by increasing [Ca2+]e from the normal value of 0.5 to 3 mM. Substitution of extracellular Cl- by isethionate, but not by NO3-, inhibited basal renin release over 20 h of incubation. NO3- also did not change renin secretion stimulated by forskolin, SNP, calmidazolium, EGTA, or by increased [Ca2+]e. Isethionate, on the other hand, markedly attenuated the effects of EGTA and of increased [Ca2+]e, but not the stimulatory effect of forskolin, calmidazolium, or SNP. Substitution of Na+ by choline also attenuated basal renin secretion and renin secretion stimulated by lowering or raising [Ca2+]e. These findings suggest that, with respect to the dependency on permeable ions, at least two different pathways of regulated renin secretion from JG cells exist: a cation- and anion-dependent Ca(2+)-related pathway and a less ion-sensitive pathway for renin secretion activated by adenosine 3',5'-cyclic monophosphate and NO.

Basolateral transport of taurine in epithelial cells of isolated, perfused Mytilus californianus gills.

We found that the basolateral surface of the gill epithelium of the marine mussel Mytilus californianus possesses a carrier-mediated process capable of concentrating taurine within epithelial cells. We used retrograde perfusion of gill sections to demonstrate the kinetics, specificity and ion-dependence of taurine transport. [3H]taurine was concentrated relative to a space marker ([14C]mannitol); this accumulation was blocked by the inclusion of 10 mmol l-1 unlabeled taurine in the perfusate. The drop in [3H]taurine uptake at increasing concentrations of unlabeled taurine was fitted to Michaelis-Menten kinetics and indicated a basolateral process with a taurine concentration at which transport is half-maximal (Kt) of 35.3 mumol l-1 and a maximal flux (Jmax) of 0.35 mumol g-1 wet mass h-1. Taurine accumulation on the apical surface had a higher affinity (Kt = 9.5 mumol l-1) and a higher maximum rate of transport (Jmax = 1.23 mumol g-1 h-1). Basolateral transport was inhibited by inclusion in the perfusate of 1 mmol l-1 of another beta-amino acid (beta-alanine), but not by inclusion of alpha-alanine, glutamic acid or betaine. The dependence of basolateral taurine transport on Na+ (when replaced with N-methyl-D-glucamine) was sigmoidal with an apparent Hill coefficient of 2.3, indicating that more than one Na+ is necessary for the transport of each taurine molecule. Complete substitution of Cl- in bathing media reduced taurine accumulation by 90% and 70% on the apical and basolateral surfaces, respectively. Taurine accumulation on both surfaces was reduced by only 20% when Cl- was reduced from 496 to 73 mmol l-1, suggesting that taurine uptake is not significantly influenced by the changes in Cl- concentration accompanying the salinity fluctuations normally encountered by mussels. We estimate that the various Na+ and Cl- gradients naturally encountered by epithelial cells are capable of providing ample energy to maintain a high intracellular concentration of taurine. We suggest that the ability of epithelial cells to accumulate taurine across the basolateral surface from the hemolymph plays a significant role in the intracellular regulation of this important osmolyte and may effect osmolality-dependent changes in the intracellular concentration of taurine.

Differential effects of extracellular anions on renin secretion from isolated perfused rat kidneys.

We investigated the relevance of anions for the regulation of renin secretion from the kidneys. For this purpose we measured renin release from isolated rat kidneys that were perfused with medium containing either 120 mmol/l (normal) chloride or 95 mmol/l of isethionate, acetate, or nitrate anions in exchange for equimolar amounts of chloride. Lowering the extracellular chloride concentration by either of these maneuvers significantly enhanced renin secretion rates (RSR) at a perfusion pressure of 100 mmHg. Increasing pressure above 100 mmHg inhibited renin release in the presence of isethionate and acetate but not with nitrate anions. The renin stimulatory effects of isethionate and acetate but not that of nitrate anions disappeared in the presence of bumetanide (100 mumol/l), an inhibitor of macula densa chloride transport. Activation of renin secretion by isethionate and acetate was blunted with 100 pmol/l angiotensin II (ANG II), whereas tenfold higher concentrations of ANG II were required to attenuate the effect of nitrate ions. The amount of renin released in the presence of nitrate was fully additive to RSR values obtained with maximally effective doses of isoproterenol. These findings are consistent with the idea that impermeant anions such as isethionate and acetate enhance renin secretion from the kidneys predominantly via the tubular macula densa mechanism. The stimulatory influence of membrane-permeable nitrate anions appears to involve additional pathways and is mediated by a decreased calcium sensitivity of the renin secretory process rather than resulting from an adenosine 3',5'-cyclic monophosphate-dependent action.

Tight-junction tightness of Necturus gall bladder epithelium is not regulated by cAMP or intracellular Ca2+. II. Impedance measurements.

In the preceding publication we have reported that, contrary to the prevailing opinion in the literature, the tight-junction tightness of Necturus gall bladder epithelium is not up-regulated by cAMP-mediated or by Ca(2+)-mediated stimulation. This conclusion was based on our observation that the stimulant-induced increase in transepithelial resistance (Rt) occurred only when the lateral intercellular spaces were allowed to collapse, which suggested that the increase reflected primarily or exclusively the increasing resistance of the lateral spaces (Rlis) rather than the postulated increase in tight-junction resistance (Rj). An alternative explanation could have been that the constancy of Rt after space dilatation reflected an increase Rj that was masked by a concomitant fall in apical and basolateral cell membrane resistances Ra and Rbl. To decide between those possibilities we have performed impedance measurements with transepithelial and intracellular microelectrodes on Necturus gall bladder epithelium. Applying previously developed analysis procedures, the measurements readily showed that elevation of intracellular Ca2+ concentration increased Rlis, but left Rj as well as Ra and Rbl quasi constant. Experiments with forskolin, theophylline or isobutylxanthine, on the other hand, were less clear. These stimulants activated an apical Cl- conductance, which drastically reduced Ra and apparently caused low-frequency polarization effects that could not be accounted for by the classical epithelial equivalent circuit. After elimination of the polarization phenomena by uni- or bilateral substitution of Cl- by isethionate or sulphate, however, we were able to demonstrate that Rj remains constant under cAMP-mediated stimulation irrespective of whether the lateral spaces are kept open or are allowed to collapse. We conclude that the tight-junction resistance of Necturus gall bladder epithelium is not controlled by intracellular Ca2+ or by cAMP-mediated stimulation.

Electric properties of rat liver cell cultures on gas-permeable membranes.

In rat hepatocytes grown on gas-permeable membranes (Petzinger et al. In Vitro Cell. Dev. Biol. 24: 491-499, 1988), cellular and canalicular potentials as well as input resistances were measured using two-channel microelectrodes. In HCO3(-)-containing solutions, we found -30.9 +/- 0.4 (SE) (n = 141) and -13.9 +/- 1.4 mV (n = 22) for cell and canalicular membrane potentials, respectively. There was no dependence of these parameters on the age of the primary culture. Canalicular input resistance, however, increased from 13.3 +/- 2.0 M omega (n = 4) at day 1 after seeding to 36.1 +/- 5.0 M omega (n = 9) at day 2 and stabilized thereafter, while cell input resistance continuously decreased from 37.0 +/- 3.3 M omega at 1 h (n = 6) to 5.2 +/- 2.1 M omega (n = 27) at 3 days after preparation. In ion substitution experiments there were no changes in the transference numbers for K+, Na+, or Cl- that could account for this effect. Cable analysis, however, revealed that the decrease in input resistance reflects a time-dependent increase in electrical coupling between cells. We conclude that rat liver cells on gas-permeable membranes are highly suited for the quantitative analysis of cell-to-cell interaction. In addition, cells and canaliculi are readily accessible with two-channel microelectrodes, making this preparation a promising tool for electrophysiological analysis of hepatocellular transport mechanisms.

The interaction between ethanol and cysteine on the central depressant effects of ethanol in mice.

In this study male Swiss-Webster mice were used to examine the effects of cysteine (ICV), a precursor in the biosynthesis of taurine, on ethanol-induced loss of the righting reflex. The interaction of ethanol with gamma-aminobutyric acid (GABA) and isethionic acid, a metabolite of taurine, was also investigated on ethanol-induced central nervous system depression as measured by loss of the righting reflex experiments. Immediately after the animals regained the righting reflex following ethanol injection (IP) mice received an ICV injection of saline, cysteine (1, 15 or 25 mumol/kg), GABA (1, 15 or 25 mumol/kg) or isethionic acid (25 or 50 mumol/kg). Upon ICV administration of cysteine or GABA the mice again lost the righting reflex. This effect occurred immediately and in a dose-dependent manner. The compound, isethionic acid, failed to cause a second loss of the righting reflex following ethanol administration (IP). In the absence of ethanol cysteine or GABA (25 mumol/kg, ICV) did not produce a substantial loss of the righting reflex in mice. In another experiment mice were pretreated (IP) with L-2-oxothiazolide-4-carboxylate (OTC) 2 hr prior to ethanol administration (IP). OTC is a compound which can be converted to cysteine in the body. In the presence of ethanol OTC (15 mmol/kg) caused an enhancement of ethanol-induced central nervous system depression under certain conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Prolactin synthesis in cultured pituitary cells is chloride-dependent.

Release of prolactin from both normal pituitary cells and rat pituitary tumor (GH) cells is an osmotic process that is dependent upon chloride. The long term growth rate of GH-cells in medium in which chloride was exchanged with isethionate was completely normal, but, by 48 h, isethionate substitution resulted in a 70% decrease in the concentration of internal and secreted prolactin. Isethionate caused a much smaller reduction in growth hormone production (less than 20%). These results suggest that exchange of chloride with isethionate is inhibiting the synthesis of prolactin. Reduction of intracellular levels of prolactin in cells grown in isethionate-containing medium was evident by 30 h, and the level of prolactin was reduced 92% at 96 h. This reduction in the internal concentrations of prolactin was reversed when the cells were returned to normal medium containing chloride with a t1/2 of 48 h. Addition of epidermal growth factor and the calcium channel agonist BAY K 8644 to cells in medium containing chloride increased internal prolactin by 400%, and isethionate exchange reduced the response by 85%. To confirm that isethionate exchange was inhibiting the synthesis of prolactin, mRNA concentrations for prolactin and actin were determined. Both basal and hormone-stimulated levels of prolactin mRNA were reduced 70 to 90% by isethionate exchange, while actin mRNA levels did not change. To determine whether the effect of isethionate was at the level of gene transcription, GH-cells were transfected with a prolactin-chloramphenicol acetyltransferase fusion gene and chloramphenicol acetyltransferase expression was assessed using cells in chloride and isethionate-containing media. Both basal and hormone-stimulated synthesis of chloramphenicol acetyltransferase driven by the prolactin promoter was inhibited by isethionate exchange. These studies demonstrate that exchange of medium chloride with isethionate inhibits the synthesis of prolactin at the level of transcription.

ATP-dependent glutamate uptake into synaptic vesicles from cerebellar mutant mice.

The ATP-dependent glutamate uptake system in synaptic vesicles prepared from mouse cerebellum was characterized, and the levels of glutamate uptake were investigated in the cerebellar mutant mice, staggerer and weaver, whose main defect is the loss of cerebellar granule cells, and the nervous mutant, whose main defect is the loss of Purkinje cells. The ATP-dependent glutamate uptake is stimulated by low concentrations of chloride, is insensitive to aspartate, and is inhibited by agents known to dissipate the electrochemical proton gradient. These properties are similar to those of the glutamate uptake system observed in the highly purified synaptic vesicles prepared from bovine cortex. The ATP-dependent glutamate uptake system is reduced by 68% in the staggerer and 57-67% in the weaver mutant; these reductions parallel the substantial loss of granule cells in those mutants. In contrast, the cerebellar levels of glutamate uptake are not altered significantly in the nervous mutant, which has lost Purkinje cells, but not granule cells. In view of evidence that granule cells are glutamatergic neurons and Purkinje cells are GABAergic neurons, these observations support the notion that the ATP-dependent glutamate uptake system is present in synaptic vesicles of glutamatergic neurons.

Localisation of the hydrophilic C terminal part of the ATP synthase subunit 8 of Saccharomyces cerevisiae.

The hydrophobic subunit 8 of the yeast ATP synthase was modified using the non-penetrating amino reactive specific reagent: isethionylacetimidate. The polypeptide was modified when using the isolated ATP synthase and sodium bromide-treated submitochondrial particles. It is shown that the only lysine of the protein was modified by the reagent. It is concluded that the hydrophilic C terminal part of the protein containing lysine 47 is located on the inner side of the inner mitochondrial membrane.

Characterization of glutamate uptake into synaptic vesicles.

Recent evidence indicates that L-glutamate is taken up into synaptic vesicles in an ATP-dependent manner, supporting the notion that synaptic vesicles may be involved in glutamate synaptic transmission. In this study, we further characterized the ATP-dependent vesicular uptake of glutamate. Evidence is provided that a Mg-ATPase, not Ca-ATPase, is responsible for the ATP hydrolysis coupled to the glutamate uptake. The ATP-dependent glutamate uptake was inhibited by agents known to dissipate the electrochemical proton gradient across the membrane of chromaffin granules. Hence, it is suggested that the vesicular uptake of glutamate is driven by electrochemical proton gradients generated by the Mg-ATPase. Of particular interest is the finding that the ATP-dependent glutamate uptake is markedly stimulated by chloride over a physiologically relevant, millimolar concentration range, suggesting an important role of intranerve terminal chloride in the accumulation of glutamate in synaptic vesicles. The vesicular glutamate translocator is highly specific for L-glutamate, and failed to interact with aspartate, its related agents, and most of the glutamate analogs tested. It is proposed that this vesicular translocator plays a crucial role in determining the fate of glutamate as a neurotransmitter.

Permeant anions are not required for norepinephrine secretion from pheochromocytoma cells.

The 'chemiosmotic' model for secretion proposed by Pollard and his colleagues (Int. Rev. Cytol. 58, 159-197, 1979) was tested with pheochromocytoma cells. Contrary to the prediction of this model, norepinephrine secretion did not require the presence of a permeant anion in the medium. Secretion was not blocked by replacing much of the Cl- of the medium with isethionate or by replacing all of the Cl- salts of the medium with isotonic sucrose. Biochemical evidence is presented to indicate that the cells secreted by the normal exocytotic mechanism in the sucrose medium. Making the normal bathing medium hypertonic with 300 mM sucrose increased the basal level of norepinephrine release, but also suppressed secretion in response to a strong secretagogue (1 mM Ba2+). The data indicate that the Pollard model does not apply to pheochromocytoma cells, but suggest the possible involvement of osmotic pressure in exocytosis.

Taurine, analogues and ethanol elicited responses.

The effect of taurine, of some of its precursors and major metabolic products on spontaneous locomotor activity were studied in mice. The effect of taurine and some analogues on certain ethanol-mediated responses were observed. Administration of taurine, 50 mg/kg, IP, did not significantly alter motility in experimental animals compared to controls. Behavioral depression was evident subsequent to injection of cysteine hydrochloride or taurocholic acid (50 mg/kg). Administration of taurocholic acid, 50 mg/kg, IP, 30 min prior to a narcotic dose of ethanol, 5 g/kg, IP, reduced the time required for the onset of ethanol-narcosis. Pretreatment with cysteic acid, 50 mg/kg, IP, prolonged ethanol-produced narcosis. Treatment with cysteic acid 30 min prior to ethanol, 2.5 g/kg, IP, was found to decrease whole blood ethanol concentration as compared to the respective controls without a concomitant changes in brain ethanol levels. Administration of taurocholic acid, 100 mg/kg, IP, decreased the intake of an ethanol solution in rats preferring 5% ethanol solution over water as the drinking fluid of choice. None of the compounds tested altered endogenous specific activity of mouse liver alcohol dehydrogenase when given once daily (50 mg/kg, IP) for 10 consecutive days. The results suggest that both taurocholic acid and cysteic acid exert additive action to some ethanol-elicited responses studied.

Oxidative phosphorylation. Halide-dependent and halide-independent effects of triorganotin and trioganolead compounds on mitochondrial functions.

1. Each of five triorganotin and five triorganolead compounds was shown to perturb mithochondrial functions in three different ways. One is dependent and two are independent of Cl- in the medium. 2. Structure-activity relationships for the three interactions are described, and compounds suitable as tools for the separate study of each process are defined. 3. In a Cl- -containing medium trimethyltin, triethyltin, trimethyl-lead, triethyl-lead and tri-n-propyl-lead all produce the same maximum rate of ATP hydrolysis and O2 uptake; this rate is much less than that produced by uncoupling agents such as 2,4-dinitrophenol. 4. Increase in ATP hydrolysis and O2 uptake are measures on energy ultilization when triogranotin and triorganolead compounds bring about an exchange of external C1- for intramitochondrial OH- ions. Possible rate-limiting steps in this process are discussed. 5. In a C1- -containing medium ATP synthesis linked to the oxidation of beta-hydroxybutyrate or reduced cytochrone c is less inhibited by triethyltin or triethyl-lead than is ATP synthesis linked to the oxidation of succinate, pyruvate or L-glutamate. 6. The inhibition of ATP synthesis linked to the oxidation of both beta-hydroxybutyrate and reduced cytochrome c consists of two processes: one is a limited uncoupling and is C1- -dependent and the other is a C1- -independent inhibition of the energy-conservation system. 7. The different sensitivities to inhibition by triethyltin of mitochondrial functions involving the oxidation of beta-hydroxybutyrate and succinate are compared and discussed.

Effect of taurine on ethanol-induced sleeping time in mice.

The CNS-depressant effect of ethanol was markedly reduced in mice by simultaneous intraperitoneal injection of taurine.