Taste assessment of individual salts in water: Methodology and preliminary findings by a selected national panel

As part of a larger study the taste rating, according to a speciallydesigned taste rating scale, of NaCl, MgCl₂, CaCl₂, NaHCO₃,Mg(HCO₃)₂, Ca(HCO₃)₂, Na₂SO₄, MgSO₄ and CaSO₄ solutions in bi-distilledwater was determined by a carefully selected panel consistingof 52 subjects. Increasing concentrations of the 9 salts resultedin quite different taste rating curves, with optima for NaHCO₃and CaSO₄. The lowest cation concentration resulting in a meantaste rating, corresponding with an objectionable taste forthe average panel member, was tentatively defined for magnesium,calcium and sodium as respectively 10, 100 and 175 mg/1. Theanions seem to exert a masking effect on the sensory detectabilityof the cations, which effect is most outspoken for the sulphate-ion.Standards for drinking water in relation to prevention of objectionablewater taste should primarily define values for the cations andnot for anions such as chloride under normal pH conditions.     

Learned aversions and taste qualities in hamsters

Interralations among taste perceptions in gloden hamsters (Mesocricetusauratus) were examined using generalizaions of learned tasteaversions. If stimulus A is avoided given a taste aversion hasbeen established to stimulus B, and vice versa, A and B ‘cross-generalize’.Stimuli within five groups cross-generalized. The groups ofcompounds were (i) sweeteners (fructose, saccharin, sucrose);(ii) sodium salts (NaCl, NaNO₃, Na₂SO₄): (iii) non-sodium salts(KCl, MgSO₄ NH₄Cl) plus quinine HCl; (iv) acids (acetic, hydrochloric,citric); and (v) urea. Only two pairs of stimuli from differentgroups cross-generalized (HCl—NH₄Cl. quinine HCl—urea).Neural patterns of response recorded form chorda tympam nervefibers in hamsters suggest that taste receptors on the anteriortongue distinguish among three groups of taste stimuli: sweeteners,sodium salts, and a group including non-sodium salts, acids,quinine HCl and urea. Neurons innervating other taste fieldsare likely to provide the information that hamsters use to discriminateamong the tastes of non-sodium-salt and non-sweetener stimuli.     

The Perception of Saltiness is Eliminated by NaCl Adaptation: Implications for Gustatory Transduction and Coding

The tastes of salts to humans are complex. NaCl is the mostpurely salty of all salts, but even this stimulus tastes sweetat low concentrations and somewhat sour at mid-range intensities.Other salts taste significantly sour or bitter in addition tosalty. Previous studies have shown that the saltiness of simplehalide salts is reduced by adaptation to NaCl, suggesting thata single mechanism might be responsible for the salty tasteof these stimuli. In electrophysiological studies in rodents,the response to NaCl is reduced by application to the tongueof the Na⁺- channel blocker amiloride. Organic Na⁺ salts aremore heavily dependent on this amiloride-sensitive transductioncomponent than NaCl, and are generally less salty and more sour.In order to investigate the relationship between NaCl saltinessand that evoked by other salts, we adapted the tongue to distilledH₂O and to 0.1 M NaCl and obtained direct magnitude estimatesof the taste intensity of 15 organic and inorganic Na⁺, Li⁺,K⁺ and Ca²⁺ salts, matched for total intensity. Subjects dividedthese magnitude estimates among the component taste qualities.Adaptation to NaCl abolished the taste of NaCl and LiCl, andeliminated the saltiness of all other salts. The magnitude estimatesof the bitterness and sourness of many salts increased afterNaCI adaptation. Since recent biophysical data suggest thatadaptation in taste receptors may involve whole-cell mechanisms,we propose that saltiness is reduced by NaCl adaptation becauseit originates in the subset of taste receptors responsive toNaCl. This implies that saltiness is coded within the CNS incells whose receptive fields include the NaCl-sensitive receptorcells and that the degree to which any salt tastes salty isdetermined by its ability to drive these receptors. This modelproposes, for example, that KCl has a salty component becauseit stimulates some of the same receptor cells as NaCl, eventhough the transduction mechanisms for KCl are different thanthose engaged by NaCl. Adaptation to NaCl blocks the saltinessof KCl and other salts because they stimulate NaCl-sensitivereceptor cells. Chem. Senses 20: 545–557, 1995.     

MAGNITUDE ESTIMATES OF GUSTATORY QUALITY CHANGES AS A FUNCTION OF SOLUTION CONCENTRATION OF SIMPLE SALTS

Concentration-dependent quality changes in inorganic salt solutionswere investigated by obtaining quality reports, and magnitudeestimates, from four subjects, of the taste of LiCl, KCl, andNaCl solutions in the concentration range from 0.004 M to 0.050M; and Li₂SO₄ and K₂SO₄ solutions in the concentration rangefrom 0.002 F to 0.025 F. Plots of the geometric mean of themagnitude estimates for each quality as a function of concentrationconfirmed the general findings of earlier investigators (Höberand Kiesow, 1898; Renqvist, 1919; Dzendolet and Meiselman, 1967).In addition, differences found among the various studies werelinked to differences in procedure which established variablelevels of subject adaptation in the studies and permitted uncontrolledwater tastes to affect the data. It was concluded that a concentration-dependentphysicochemical change in the salt solutions, as proposed byDzendolet (1968), combines with a water taste to produce thequality of low concentration inorganic salt solutions. The relativecontribution of these two mechanisms to the overall qualityof the solution at any concentration will depend on the proceduresemployed. ^* Reprint requests should be sent to present address: John B.Pierce Foundation Laboratory, 290 Congress Ave., New Haven,CT 06519.     

Are the Tastes of Polycose and Monosodium Glutamate Unique?

To study whether Polycose and monosodium L-glutamate (L-MSG)have unique tastes differing from the traditional four basictastes, chemosensory profiles were established for Polycose,L-MSG and a group of related compounds (sucrose, maltose, monosodiumD-glutamate (D-MSG), sodium chloride, calcium chloride). Flavourswere assessed using whole-mouth tests in human subjects withnose open or clamped to reduce olfactory input. Polycose (amixture of glucose-based oligosaccharides) had a flavor consistingof an olfactory component and a maltose-like taste. L-MSG andD-MSG profiles differed from each other, and from NaCl and CaCl₂.L-MSG had a lower threshold and a higher frequency of ‘other’tastes than the D form. The data do not support a ‘polysaccharide’taste, but suggest a chiral receptor site for ‘umami’taste. Chem. Senses 21: 341–347, 1996.     

Effects of selective adaptation on coding sugar and salt tastes in mixtures

Little is known about coding of taste mixtures in complex dynamic stimulus environments. A protocol developed for odor stimuli was used to test whether rapid selective adaptation extracted sugar and salt component tastes from mixtures as it did component odors. Seventeen human subjects identified taste components of "salt + sugar" mixtures. In 4 sessions, 16 adapt-test stimulus pairs were presented as atomized, 150-μL "taste puffs" to the tongue tip to simulate odor sniffs. Stimuli were NaCl, sucrose, "NaCl + sucrose," and water. The sugar was 98% identified but the suppressed salt 65% identified in unadapted mixtures of 2 concentrations of NaCl, 0.1 or 0.05 M, and sucrose at 3 times those concentrations, 0.3 or 0.15 M. Rapid selective adaptation decreased identification of sugar and salt preadapted ambient components to 35%, well below the 74% self-adapted level, despite variation in stimulus concentration and adapting time (<5 or >10 s). The 96% identification of sugar and salt extra mixture components was as certain as identification of single compounds. The results revealed that salt-sugar mixture suppression, dependent on relative mixture-component concentration, was mutual. Furthermore, like odors, stronger and recent tastes are emphasized in dynamic experimental conditions replicating natural situations.     

Psychophysical evidence that oral astringency is a tactile sensation

Aluminum potassium sulphate [AIK(SO₄)₂ 12H₂O—‘alum’]was tested for its ability to elicit oral astringency independentlyof its ability to elicit taste. First, the astringency producedby alum (10 g/l; 21.1 mM) on the non-gustatory surfaces betweenthe gum and the upper lip was measured. Subjects reported thatalum elicited sensations of astringency when the upper lip wasmoved laterally against the gum. Second, subjects dipped thetongue into two solutions—alum or a mixture solution thatapproximated the taste of alum—and attempted to determinewhich solution was more astringent. A slight tendency was foundfor subjects to identify the mixture as more astringent thanthe alum. However, the same subjects reported the alum to bemore astringent than the mixture when the same solutions wereapplied under the upper lip. These two experiments support thehypothesis that tactile stimulation is important for producingastringency, whereas taste stimulation of the anterior tongueis not. Third, after the application of alum, lubricating rinses(water, sucrose, Salivart®, corn oil, and the subjects'own saliva) were compared for their ability to decrease astringency.The lubricants reliably decreased original astringency, butto varying degrees depending upon their lubricating properties.All three experiments suggest that tactile sensations causedby increased friction (decreases,in salivary lubrication) betweenoral membranes are the primary basis of astringent sensations.     

Inhibition of hamster chorda tympani neural response by copper chloride

Copper chloride was evaluated as a specific inhibitor of neuralresponses to sweet taste stimuli in the goldern hamster (Mesocricetusauratus). The chorda tympani whole-nerve response to taste stimuliwas recorded before and after the tongue was treated for 30s with 0.01, 0.1 and 1 mM CuCl₂. Sweet stimuli [sucrose, fructose,saccharin (calcium salt), D-phenylalanine], which primarilystimulate chorda tympani S fibers, and non-sweet stimuli (NaCl,NH₄Cl) were used. At 0.01 mM, copper chloride had little effect.At 0.10 mM it partially inhibited responses to sucrose and saccharin,but had little effect on responses to D-Phe, fructose, NaCl,NH₄Cl, or a mixture of sucrose plus L-Phe. L-Phe, which hasthe same chelating properties as D-Phe, is not an S-fiber stimulusand likely reduced sucrose inhibiton by chelating the cupricion.Analysis of concentration–response functions revealedthat 0.1 mM copper chloride inhibited the neural response tolow concentrations of sucrose by about 25%, but did not significantlyinhibit high concentrations of surcrose, suggesting competitiveinhibition. In contrast, 0.1 mM CuCl₂ reduced saccharin responsesby 25% throughtout the effective range, suggesting non-competitiveinhibition. Occupation of a saccharide receptor site by coppermay interfere with dimer but not monomer reception and distortthe saccharin receptor site. At 1 mM, CuCl₂ non-competitivelyinhibited responses to sucrose, fructose, saccharin and thenon-sweet NaCl (an N-fiber stimulus), but not NH₄Cl (an H-fiberstimulus). The mechanisms of copper chloride inhibition aredifficult to establish because its effects are weak at concentrationswhere they are specific.     

The effect of salinity on glucose absorption and incorporation by pea roots

Osmotic adaptation was observed in pea plants grown in Na₂SO₄salinized media but no complete adaptation was observed in plantsgrown in NaCl salinized media. The absorption of externally supplied glucose was depressedin pea root tips from plants grown in media salinized with eitherNaCl or Na₂SO₄. Under NaCl salinity this depression increasedwith increasing salinity. Under Na₂SO₄ salinity, no significantinhibition of absorption was observed in roots exposed to waterpotentials higher than –5 atmosphere. The amount of ¹⁴Creleased as CO₂, expressed as the percent of absorbed ¹⁴C, increasedwith increasing salinity of both types. In roots grown underNaCl salinity, the incorporation of ¹⁴C into ethanol non-soluble,acid hydrolyzable substances was markedly inhibited. This inhibitionwas increased by increasing the external salinity. The effectof Na₂SO₄ salinity was similar but not so pronounced. The incorporation of ¹⁴C from externally supplied glucose intothe alkali-soluble fraction was practically uneffected by salinity.Non-extractable ¹⁴C was decreased in roots exposed to NaCl butwas not, apparently, effected by Na₂SO₄). Because of the smallnessof this fraction no clear cut conclusion can be made. Possiblemechanisms for the events are discussed. (Received October 26, 1972; )     

Effects of Na2SO4, K2SO4 and KCl on Growth and Ion Uptake of Callus Cultures of Vaccinium corymbosum L. cv. Blue Crop

Non-selected and Na₂SO-, K₂SO₄- or KCl-selected callus culturesof Vaccinium corymbosum L. cv. Blue Crop were grown on mediasupplemented with 0, 25 and 50 mM Na₂SO₄ (non-selected and Na₂SO(-selectedonly), 0, 25 and 50mMK₂SO₄ (non-selected and K₂SO₄-selectedonly) or 0, 50 and 100 mM KCl (non-selected and KCl-selectedonly). On all media, growth of selected callus (on a fresh-weightor dry-weight basis) was greater than that of non-selected callus,and selected callus grew optimally on the level and type ofsalt on which it was selected. Selected callus was friable andmaintained a higher f. wt:d. wt ratio. Tissue water potentialin selected callus was more negative than in non-selected callus. Flame photometry and chloridometry showed Na⁺, K⁺ and Cl^–accumulated in callus to concentrations equal to or greaterthan the initial concentration in the medium. Turbidometry showedthat tissue SO₄^2- concentration was lower than the concentrationin the medium. In most cases selected callus accumulated moreNa⁺, K^sup, SO₄^2– or Cl^– than non-selected callus.Vacuolar ion concentration was measured by electronprobe X-raymicroanalysis, and on most media selected callus had highervacuolar ion concentrations than non-selected callus. SO₄^2–and Cl^– were accumulated in the vacuoles at concentrationshigher than the external medium, but vacuolar Na⁺ concentrationdid not reach external concentration on Na₂SO₄ and on potassiumsalts was maintained between 12 and 17 mM. Vacuolar K⁺ concentration(approx. 142–191 mM on no salt) decreased on Na₂SO₄ andincreased on K₂SO₄ and KCl. There was no precise correlation between total or specific ionaccumulation (Na⁺, K⁺, SO₄^2– and Cl^– and fresh-weightyield. Results suggest that selection results in adaptationin response to decreased water potential of the medium. Vaccinium corymbosum, blueberry, electronprobe X-ray microanalysis, callus, in vitro selection, salt tolerance, KCl, K₂SO₄, Na₂SO₄     

Aqueous two-phase extraction coupled with ultrafiltration for purification of amyloglucosidase

Aqueous two phase extraction (ATPE) in combination with ultrafiltration was employed for concentration and purification of amyloglucosidase produced by solid state fermentation. After extraction (with water) from dry moldy bran the dilute enzyme extract was concentrated by ATPE in a polyethylene glycol (PEG)/maltodextrin (MDX) system. The enzyme in the top PEG rich phase was then extracted into a Na₂HPO₄ rich bottom phase and further concentrated by ultrafiltration. The partitioning behavior of amyloglucosidase was examined in PEG/MDX, PEG/Na₂SO₄, PEG/Na₂HPO₄, PEG/KH₂PO₄ aqueous two phase systems. Effect of buffering salts such as NaCl, Na₂HPO₄, KH₂PO₄ and Na₂SO₄ on the partitioning behavior of enzyme was studied in PEG/MDX system. Maximum partitioning of amyloglucosidase was seen with KH₂PO₄ (m = 18.1). A two stage ATPE employing PEG/MDX (buffered with KH₂PO₄) and PEG/Na₂HPO₄ systems, followed by ultrafiltration has resulted in an overall recovery of 78.4% with 3.1 fold purification and 9.4 fold concentration of the enzyme.     

Functional Aspects of the Salt Glands of the Plumbaginaceae

X-ray microanalysis and diffuse reflectance infrared Fouriertransform spectrometry were used to determine the presence andratios of elements in salt secretions from salt glands of greenhouseand experimentally-manipulated leaves of five species of thePlumbaginaceae Sodium, magnesium, silica, sulphur, phosphorus,chloride, potassium, calcium and carbonate were detected insecretions of greenhouse-grown plants. The salt glands of excisedleaves challenged by solutions of KI, KCl, NaCl, Na₂SO₄, MgCl₂and MgSO₄ secreted principally the ions of the challenging solutions. Key words: Ion transport, secretion     

Effects of altered tonicity by sodium chloride on L-tryptophan binding to hepatic nuclei

This study was concerned with theeffects of NaCl administered in vivo or added in vitro to isolatednuclei on [³H]tryptophan binding to rat hepaticnuclei assayed in vitro. Hypertonic (10.7%) NaCl administered in vivoto rats caused at 10 min a marked decrease in in vitro binding (totaland specific) of [³H]tryptophan to hepaticnuclei. In vitro incubation of isolated hepatic nuclei, but not ofisolated nuclear envelopes, with added NaCl (particularly at 0.125 × 10⁴ M and 0.25 × 10⁴ M) revealed significant inhibition of[³H]tryptophan binding. However, isolatedhepatic nuclear envelopes prepared after in vitro incubation ofisolated nuclei with added NaCl did show inhibition of[³H]tryptophan binding (total and specific)compared with controls. Other salts (KCl, MgCl₂,NaHCO₃, NaC₂H₃O₂, NaF,or Na₂SO₄), at similar concentrations to thatof NaCl except for MgCl₂, when added to isolated nuclei didnot appreciably inhibit nuclear tryptophan binding. Kinetic studies ofin vitro nuclear [³H]tryptophan binding in thepresence of 0.125 × 10⁴ M NaCl revealed thatbinding decreased at 0.5 h and continued to 2 h compared with nuclear[³H]tryptophan binding with controls (withoutNaCl addition). The results obtained in vivo in rats and those obtainedin vitro with isolated hepatic nuclei revealed NaCl-induced inhibitoryeffects on [³H]tryptophan binding to hepaticnuclei. Although the inhibitory effects were similar under the twodifferent experimental conditions, the mechanism for each may bedifferent in that the NaCl concentration in hepatic cells afteradministration of NaCl in vivo was appreciably higher than the lowlevels added in vitro to the isolated hepatic nuclei.

     

Binary taste mixture interactions in prop non-tasters, medium-tasters and super-tasters

It is generally assumed that the mutual, but asymmetric, suppression of the components in binary taste mixtures is an invariant property of the human psychophysical response to such mixtures. However, taste intensities have been shown to vary as a function of individual differences in sensitivity, indexed by the perceived bitterness of 6-n-propylthiouracil (PROP). To determine if these variations in taste perception influence taste mixture interactions, groups of PROP super-, medium- and non-tasters assessed four binary taste mixtures: sweet-bitter [sucrose/quinine hydrochloride (QHCl)], sweet-sour (sucrose/citric acid), salty-bitter (NaCl/QHCl) and salty-sour (NaCl/citric acid). In each experiment, subjects received factorial combinations of four levels of each of two tastants and rated individual taste intensities and overall mixture intensity. For each taste quality, super-tasters typically gave higher ratings than either medium- or non-tasters, who tended not to differ. There were also group differences in the interactions of the mixtures' components. Super-tasters rated the overall intensity of the mixtures, most likely reflecting integration of the taste components, as greater than medium- and non-tasters, who again showed few differences. In sweet-bitter mixtures, non-tasters failed to show the suppression of sweetness intensity by the highest QHCl concentration that was evident in super- and medium-tasters. These data show that the perception of both tastes and binary taste mixture interactions varies as a function of PROP taster status, but that this may only be evident when three taster groups are clearly distinguished from one another.     

Generalization of learned taste aversions in rabbits: similarities among gustatory stimuli

Although rabbits have been used in a number of electrophysiologicaland anatomical studies on the gustatory system, there have beenfew behavioral experiments on these animals and these have beenlimited to studies of taste preference. The similarities amonga number of gustatory stimuli were assessed in rabbits by measuringthe generalization patterns in a conditioned taste aversionexperiment. Rabbits were trained to take their daily rationof water within a 30-min session, during which the number oflicks per 10-s presentation of a drinking tube could be recorded.During one of these sessions, one of 12 stimuli (sucrose, fructose,Na-saccharin, NaCI, NaNO₃, Na₂SO₄, KC1, NH₄C1, CaCl₂, HC1, QHC1or urea) was presented, followed by i.p. injection of LiCl toproduce a conditioned taste aversion. Animals were then testedwith all of the stimuli and the amount of suppression of lickingwas used as a measure of stimulus generalization. The patternsof generalization were compared for the test and conditioningstimuli separately. Some nonreciprocities were seen betweenthe conditioning and test stimuli, which reflected the occurrenceof multiple taste qualities and the tendency for aversions togeneralize more to stronger stimuli than to weaker ones. Principalcomponents analysis of the stimulus relationships showed thatrabbits responded to these stimuli in a fashion similar to thatof other mammals, including humans. Within the principal componentssolution, there were strong similarities among the sugars, thesodium salts, the nonsodium salts and the bitter-tasting stimuli.     

Lactic acid content and formation in pea roots exposed to salinity

Lactic acid content and production, as well as lactic dehydrogenaseactivity were studied in pea root tips grown in media salinatedwith NaCl or Na₂SO₄. Salinity of both types depressed the lacticacid content of the tissue. Lactic dehydrogenase activity linkedto NADH was depressed by high concentrations of NaCl in thegrowth medium, but was stimulated by increasing concentrationsof Na₂SO₄. There was a trace of NADPH linked activity of theenzyme; this activity was not affected by chloride salinitybut was depressed by sulphate salinity. It is not yet clearhow these events are connected with the overall effect of salinityon the carbohydrate metabolism of pea root tips. (Received June 27, 1970; )     

Changes in the levels of jasmonates and free polyamines induced by Na<Subscript>2</Subscript>SO<Subscript>4</Subscript> and NaCl in roots and leaves of the halophyte <Emphasis Type="Italic">Prosopis strombulifera</Emphasis>

Prosopis strombulifera, a common legume in high-salinity soils of Argentina, is a useful model for elucidation of salt tolerance mechanisms and specific biochemical pathways in halophytes, since its NaCl tolerance exceeds the limit described for most halophytic plants. We analyzed the effects of the increasing concentration of two main soil salts, Na₂SO₄ and NaCl, on growth parameters of P. strombulifera, chlorophyll levels, and content of jasmonates (JAs) and polyamines (PAs), which are key molecules involved in stress responses. P. strombulifera showed a halophytic response (growth promotion) to NaCl, but strong growth inhibition by iso-osmotic solutions of Na₂SO₄. Chlorophyll levels, number of leaves and leaf area were also differentially affected. An important finding was the partial alleviation of SO₄²⁻ toxicity by treatment with two-salt mixture. JAs are not directly involved in salt tolerance in this species since its levels decrease under all salt treatments. Beneficial effects of Putrescine (Put) accumulation in NaCl treated plants maybe inferred probably associated with the antioxidative defense system. Another novel finding is the accumulation of the uncommon PA cadaverine in roots under high Na₂SO₄, which may be related to SO₄²⁻ toxicity.     

The taste of sodium chloride: masking and adaptation

Human subjects estimated the saltiness of sodium chloride anda mixture of sodium chloride and sucrose. The adapting effectsof sucrose, sodium chloride and a mixture of both substanceswere investigated. The stimuli were delivered by a flow systemto pre-defined tongue areas. After adaptation to NaCl and tothe mixture the subjective intensity of NaCl-saltiness decreased58% and 69% respectively. Also a strong masking effect of saltinesswas observed: 59.1% reduction. No indications of crossadaptationwere found. The results were interpreted in favour of the independencyof adaptation and masking.     

Ingestive responses to some heavy metal salts in mice and inhibition of taste nerve responses by metals

Preference-aversion for heavy metals in ddy mice was examinedusing the two-bottle preference technique. Mice preferred MnCl₂,CoCl₂ at certain concentration ranges, but avoided NiCl₂, CuCl₂,ZnCl₂ and CdCl₂. The avoidance threshold for the salts becamelower in the order of Mn > Co > Ni > Cd > Cu >Zn, though the degree of rejection for CuCl₂ was larger thanthat for ZnCl₂. Preferences for sucrose and Na saccharin werereduced by low concentrations of CuCl₂ or ZnCl₂. However, preferencefor glycine was scarcely affected by addition of either saltat 1 mM. Electrophysiological experiments in mice on the inhibitionby heavy metal salts of chords tympani nerve responses to thefour basic taste stimuli revealed that CuCl₂ and ZnCl₂ at 1mM inhibited the response to sucrose strongly and those to guinineHCl (QHCl) and NaCl moderately, but had no effect on the HClresponse. On the other hand, MnCl₂, CoCl₂ and NiCl₂ at 1 mMscarcely inhibited the response to sucrose but suppressed thoseto other stimuli. CoCl₂ moderately inhibited responses to allthe stimuli. In general, metal salts producing a larger inhibitionof neural responses to sucrose and QHCL are avoided by miceat a lower concentration.     

Stimulation of RNA Synthesis in Isolated Nuclei by Auxin-Binding Proteins-I and -II

The auxin-binding proteins (ABP-I and ABP-II) purified frometiolated mung bean seedlings stimulated RNA synthesis in isolatednuclei both in the presence and absence of (NH₄)₂SO₄. In theabsence of (NH₄)₂SO₄, maximum stimulation of RNA synthesis occurredat 100 µg ABP-I (25%) and 300 µg ABP-II (60%), whereasin the presence of 50 mM (NH₄)₂SO₄ maximum stimulation occurredat 60 µg ABP-I (10%) and 100 µg ABP-II (40%). Thesestimulatory effects on RNA synthesis by ABP-I and ABP-II werecompletely abolished by the addition of -amanitin (4 µg/0.5ml reaction mixture). IAA had no effect on the stimulation ofRNA synthesis by ABP-I and ABP-II. (Received September 30, 1985; Accepted March 5, 1986)