Isotonic KCl Solution Research Articles

Stimulation of potassium cycling in mitochondria by long-chain fatty acids

Nonesterified long-chain fatty acids (myristic, palmitic, oleic and arachidonic), added at low amounts (around 20 nmol/mg protein) to rat liver mitochondria, energized by respiratory substrates and suspended in isotonic solutions of KCl, NaCl, RbCl or CsCl, adjusted to pH 8.0, induce a large-scale swelling followed by a spontaneous contraction. Such swelling does not occur in alkaline solutions of choline chloride or potassium gluconate or sucrose. These changes in the matrix volume reflect a net uptake, followed by net extrusion, of KCl (or another alkali metal chloride) and are characterized by the following features: (1) Lowering of medium pH from 8.0 to 7.2 results in a disappearance of the swelling-contraction reaction. (2) The contraction phase disappears when the respiration is blocked by antimycin A. (3) Quinine, an inhibitor of the K +/H + antiporter, does not affect swelling but suppresses the contraction phase. (4) The swelling phase is accompanied by a decrease of the transmembrane potential and an increase of respiration, whereas the contraction is followed by an increase of the membrane potential and a decrease of oxygen uptake. (5) Nigericin, a catalyst of the K +/H + exchange, prevents or partly reverses the swelling and partly restores the depressed membrane potential. These results indicate that long-chain fatty acids activate in liver mitochondria suspended in alkaline saline media the uniporter of monovalent alkali metal cations, the K +/H + antiporter and the inner membrane anion channel. These effects are presumably related to depletion of mitochondrial Mg 2+, as reported previously [Arch. Biochem. Biophys. 403 (2002) 16], and are responsible for the energy-dissipating K + cycling. The uniporter and the K +/H + antiporter are in different ways activated by membrane stretching and/or unfolding, resulting in swelling followed by contraction.

Intrinsic H(+) ion mobility in the rabbit ventricular myocyte.

The intrinsic mobility of intracellular H(+) ions was investigated by confocally imaging the longitudinal movement of acid inside rabbit ventricular myocytes loaded with the acetoxymethyl ester (AM) form of carboxy-seminaphthorhodafluor-1 (carboxy-SNARF-1). Acid was diffused into one end of the cell through a patch pipette filled with an isotonic KCl solution of pH 3.0. Intracellular H(+) mobility was low, acid taking 20-30 s to move 40 microm down the cell. Inhibiting sarcolemmal Na(+)-H(+) exchange with 1 mM amiloride had no effect on this time delay. Net H(+)(i) movement was associated with a longitudinal intracellular pH (pH(i)) gradient of up to 0.4 pH units. H(+)(i) movement could be modelled using the equations for diffusion, assuming an apparent diffusion coefficient for H(+) ions (D(H)(app)) of 3.78 x 10(-7) cm(2) s(-1), a value more than 300-fold lower than the H(+) diffusion coefficient in a dilute, unbuffered solution. Measurement of the intracellular concentration of SNARF (approximately 400 microM) and its intracellular diffusion coefficient (0.9 x 10(-7) cm(2) s(-1)) indicated that the fluorophore itself exerted an insignificant effect (between 0.6 and 3.3 %) on the longitudinal movement of H(+) equivalents inside the cell. The longitudinal movement of intracellular H(+) is discussed in terms of a diffusive shuttling of H(+) equivalents on high capacity mobile buffers which comprise about half (approximately 11 mM) of the total intrinsic buffering capacity within the myocyte (the other half being fixed buffer sites on low mobility, intracellular proteins). Intrinsic H(+)(i) mobility is consistent with an average diffusion coefficient for the intracellular mobile buffers (D(mob)) of ~9 x 10(-7) cm(2) s(-1).

The Existence of the K+ Channel in Plant Mitochondria

In this study, evidence is given that a number of isolated coupled plant mitochondria (from durum wheat, bread wheat, spelt, rye, barley, potato, and spinach) can take up externally added K(+) ions. This was observed by following mitochondrial swelling in isotonic KCl solutions and was confirmed by a novel method in which the membrane potential decrease due to externally added K(+) is measured fluorimetrically by using safranine. A detailed investigation of K(+) uptake by durum wheat mitochondria shows hyperbolic dependence on the ion concentration and specificity. K(+) uptake electrogenicity and the non-competitive inhibition due to either ATP or NADH are also shown. In the whole, the experimental findings reported in this paper demonstrate the existence of the mitochondrial K(+)(ATP) channel in plants (PmitoK(ATP)). Interestingly, Mg(2+) and glyburide, which can inhibit mammalian K(+) channel, have no effect on PmitoK(ATP). In the presence of the superoxide anion producing system (xanthine plus xanthine oxidase), PmitoK(ATP) activation was found. Moreover, an inverse relationship was found between channel activity and mitochondrial superoxide anion formation, as measured via epinephrine photometric assay. These findings strongly suggest that mitochondrial K(+) uptake could be involved in plant defense mechanism against oxidative stress due to reactive oxygen species generation.

A method for measuring resting and action potentials with external electrodes in crayfish giant axons

The true resting membrane potential and membrane action potential of crayfish giant axons were recorded with two external electrodes using a partition method in which the insulation grade was extensively improved by utilizing a water-absorbing particle mixed with vaseline and liquid paraffin, and the residual membrane potential at the lateral reference pool was removed by using an offset solution. The offset solution contained 10-4M of ouabain to block electrogenic sodium pump and a higher potassium concentration than that of the isotonic KCl solution. No short circuiting correction was necessary within an error of a few percent. Elimination of chloride ions from the offset solution substantially prolonged the surviving time of the preparation. This experimental system was developed to study a cell in as intact condition as possible, especially in a long-term experiment.

An inactivating inward-rectifying K current present in prolactin cells from the pituitary of lactating rats.

Primary cultures containing a high percentage of lactotrophs were obtained by dissociating the pituitary of rats following 14-18 days of lactation. Lactotrophs with a distinctive appearance were recorded after 1-35 days in vitro and identified by immunocytochemical staining for prolactin. Whole-cell voltage clamp measurements in isotonic KCl solution from a holding potential of -40 mV revealed the presence of inward-rectifying K currents with a time-dependent, Na(+)-independent inactivation at potentials negative to -60 mV. The time for complete inactivation was strikingly different between lactotrophs, varying between 1 sec and more than 5 sec at -120 mV, and was not related to time in culture. The reversal potential shifted 59 mV (25 degree C) for a tenfold change in external K+ concentration, demonstrating the selectivity of the channel for K+ over Na+. The inward-rectifying K current was blocked by 5 mM Ba2+ and partially blocked by 10 mM TEA. Chloramine-T (1 and 2 mM) produced a total block of the inward-rectifying K current in lactotrophs. Thyrotropin-releasing hormone (500 nM) significantly reduced the inward-rectifying K current in about half of the lactotrophs. This current is similar to the inward-rectifying K current previously characterized in clonal somatomammotrophic pituitary cells (GH3B6). The variability of the rate of inactivation of this current in lactotrophs and its responsiveness to TRH is discussed.

Involvement of Ca2+ influx-induced Ca2+ release in contractions of intact vascular smooth muscles.

Application of Ca2+ (0.1-2.5 mM) to guinea pig aortas incubated in Ca(2+)-free isotonic KCl solution induced a contraction (Ca contraction), a part of which depended on preloading the intracellular stores with Ca2+ and which was sensitive to 3 x 10(-5) M ryanodine. Because 45Ca2+ influx from the external fluid upon the addition of Ca2+ was not modified either by the state of filling of the Ca2+ store or by the presence of ryanodine, the ryanodine-sensitive component of the contraction could be attributed to the Ca2+ influx-induced Ca2+ release from the Ca2+ store. Supporting the possibility of involvement of Ca(2+)-induced Ca2+ release, the Ca contraction due to 0.1 mM Ca2+ was enhanced either by decreasing Mg2+ in the medium or by low temperature. The ratio of the ryanodine-sensitive fraction in the Ca contraction was inversely related to the concentration of Ca2+ added and also to the extent of 45Ca2+ influx. When the Ca2+ influx was decreased by verapamil or cadmium, the ratio of ryanodine-sensitive fraction increased. On the contrary, an increase of Ca2+ influx by CGP-28392 decreased the ratio. These results suggest that Ca2+ influx at a physiological level triggers Ca2+ release from the Ca2+ store, resulting in the amplification of contractile force.

Heart mitochondrial creatine kinase revisited: The outer mitochondrial membrane is not important for coupling of phosphocreatine production to oxidative phosphorylation

The state of mitochondrial creatine kinase (CKmi-mi) in intact dog heart mitochondria and mitoplasts and the mechanism of its functional coupling with the oxidative phosphorylation system have been reinvestigated under different osmotic conditions and ionic compositions of the medium. It has been established that in a medium which mimics the cardiac cell cytoplasm, dissociation of CKmi-mi from the membrane of mitoplasts increases when the mitoplasts are swollen due to hypoosmotic treatment. It was shown by EPR that hypoosmotic treatment results in the enhancement of the mobility of phospholipids in the membrane bilayer. It has been also shown that when CKmi-mi is detached from the inner membrane in intact mitochondria in isotonic KCl solution, the effects of the coupling between CKmi-mi and oxidative phosphorylation via ATP ADP translocase disappear in spite of the presence of CKmi-mi in the intermembrane space and intactness of the outer mitochondrial membrane. Therefore, this coupling cannot be explained by the “compartmented coupling” mechanism or “dynamic adenine nucleotide compartmentation” in the intermembrane space due to diffusion limitation for adenine nucleotides through the outer mitochondrial membrane, as has been supposed by several authors ( F. N. Gellerich et al. (1987) Biochim. Biophys. Acta 890, 117–126 ; S. P. J. Brooks and C. H. Suelter (1987) Arch. Biochem. Biophys. 253, 122–132 ). The data obtained show that the displacement of the enzyme from the membrane results in significantly increased sensitivity of the coupled processes of aerobic phosphocreatine synthesis to inhibition by the product, phosphocreatine. Thus, all results show that under physiological osmotic and ionic conditions CKmi-mi remains firmly attached to the inner mitochondrial membrane and effectively coupled with ATP ADP translocase due to intimate dynamic interaction between those proteins.

Tectorial membrane I: Static mechanical properties in vivo

Although the tectorial membrane in the mammalian cochlea plays a crucial role in hair-cell stimulation, its mechanical properties have never been investigated under conditions approximating those under which it normally functions. For this reason, we performed such investigations in live Mongolian gerbils. Access to the tectorial membrane was gained through the lateral wall in the second cochlear turn. As far as possible, sodium ions were kept away from the tectorial membrane by avoiding injury to Reissner's membrane, relieving the perilymphatic pressure and rinsing the scala media with an isotonic KCl solution. The tectorial membrane was manipulated with a flexible micropipette in three, approximately orthogonal, directions. Under these conditions the membrane was found to be highly compliant and resilient and to have a relatively high tensile strength. Its viscosity was low. Some of these attributes were altered by sodium ions, dyes, or death.

Voltage-independent catecholamine release mediated by the activation of muscarinic receptors in guinea-pig adrenal glands.

1. The differences between the mechanisms of muscarinic and nicotinic receptor-mediated catecholamine secretion with respect to their dependence on voltage changes and extracellular Ca were examined using perfused adrenal glands of the guinea-pig. 2. Acetylcholine (ACh, 10(-6) to 10(-3) M) caused a dose-dependent increase in catecholamine secretion. The ED50 value for ACh was 7 x 10(-5) M. In the presence of atropine (10(-5) M), the dose-response curve for ACh was shifted to the right. Hexamethonium (5 x 10(-4) M) preferentially reduced the responses to higher concentrations of ACh (greater than 10(-5) M). Pilocarpine (5 x 10(-4) M) and nicotine (3 x 10(-5) M) also stimulated catecholamine release. 3. During perfusion with isotonic KCl solution, ACh and pilocarpine, but not nicotine, evoked catecholamine secretion. These responses were abolished by atropine (10(-6) M). Pilocarpine-stimulated catecholamine secretion was enhanced during perfusion with isotonic KCl solution. Under these conditions, hexamethonium (10(-3) M) significantly augmented ACh-evoked catecholamine release. 4. During perfusion with either Ca-free isotonic KCl or Ca-free Locke solution, ACh and pilocarpine caused a partial increase in catecholamine secretion whereas nicotine and high K solution (56 mM) did not. The responses to ACh and pilocarpine were completely inhibited by atropine but not by hexamethonium. 5. When guinea-pig adrenal glands were perfused with isotonic KCl solution containing 2.2 mM Ca which was subsequently removed and replaced with EGTA, ACh-induced catecholamine secretion was similar in magnitude to that observed during perfusion with Locke solution. 6. We conclude that both nicotinic and muscarinic receptors are involved in ACh-induced catecholamine secretion from guinea-pig adrenal chromaffin cells. Activation of muscarinic or nicotinic receptors appears to stimulate catecholamine release through different mechanisms with respect to both voltage-dependence and Ca requirements.

Action potentials and net membrane currents of isolated smooth muscle cells (urinary bladder of the guinea-pig)

Cells were isolated by incubating chunks of tissue from the urinary bladder of the guinea-pig in a high potassium, low chloride medium containing 0.2 mM calcium plus the enzymes collagenase and pronase. After isolation, the cells were superfused with a physiological salt solution (PSS) containing 150 mM NaCl, 3.6 mM CaCl2 and 5.4 mM KCl (35 degrees C). Patch electrodes filled with an isotonic KCl-solution were used for whole cell recordings. With a single electrode voltage clamp we measured a capacitance of 50 +/- 5 pF per cell, an input resistance of 200 +/- 25 kOhm X cm2 and a series resistance of 44 +/- 4 Ohm X cm2. The cells had resting potentials of -52 +/- 2 mV. They did not beat spontaneously but responded to stimuli with single action potentials (APs) which rose from the threshold (-38 mV) with a maximal rate of 6.5 +/- 1.8 V/s to an overshoot of 22 +/- 3 mV. The AP lasted for 36 +/- 4 ms (measured between threshold and -40 mV). Continuous cathodal current produced repetitive activity, a pacemaker depolarization followed the AP and preceded the next upstroke. Net membrane currents evoked by clamp steps to positive potentials were composed of an inward and an outward component. The inward component generating the upstroke of the AP was carried by Ca ions (iCa, Klöckner and Isenberg 1985). The repolarization resulted from a potassium outward current iK. Ca-channel blockers (5 mM NiCl2) reduced iK suggesting that (part of) iK was Ca-activated. iK rose within about 100 ms to a peak of 40-200 muA/cm2 from which it inactivated slowly and incompletely. The inactivating iK followed a bell-shaped voltage-dependence, the noninactivating iK an outwardly rectifying one. Both parts had similar steady state inactivation curves with a half maximal inactivation potential at -36 mV and a slope of 9 mV. Repolarization to -50 mV induced outward tail currents which reversed polarity at -85 mV (the calculated potassium equilibrium potential). The amplitude and the time course of the envelope of the tail currents varied in proportion to iK during the prestep. Thus, the tail current is suggested to reflect the turning off of a potassium conductance which had been activated during the prepulse. iK was largely reduced but not blocked by 20 or 150 mM tetraethylammonium (TEA). TEA did not significantly change the resting potential, but it prolonged the AP and facilitated upstroke and overshoot.(ABSTRACT TRUNCATED AT 400 WORDS)

カダヤシ黒色素胞のアドレナリン性受容体の特性

The effects of catecholamines on the melanophores of isolated scale of Gambusia affinis affinis were investigated microscopically.In higher concentrations, catecholamines induced melanosome aggregation. Noradrenaline was most effective. Their effects were inhibited by phentolamine, an adrenergic α-blocking agent.On the other hand, catecholamines in lower concentrations induced melanosome dispersion on the melanophores of white-adapting fish. Adrenaline was most effective. Each catecholamine gave its maximum effect at the concentration of 10-10M. Propranolol, an adrenergic β-blocking agent, inhibited the dispersing effects of catecholamines. Isoproterenol, which is known to be a beta agonist, was less effective in both aggregating and dispersing melanosomes than other amines.In present study, the effect of K+ was also investigated. Melanosomes were aggregated by the application of isotonic KCl solution, and its effect was inhibited by phentolamine. 10-10M adrenaline was found to be able to disperse the melanosomes aggregated by isotonic KCl solution, but 10-10M noradrenaline was not.These results show that aggregation of melanosomes is mediated by α-adrenergic receptors and dispersion of those by β-adrenergic receptors, suggesting that α-receptors may be related to nervous control system of melanophores, and β-receptors to humoral one.

Effect of temperature on acetylcholine - induced contraction of isolated rat tracheal muscle

The tracheal strip-chain preparation of the rat was used to study the effect of temperature on electrically or acetylcholine (ACh)- induced contraction. The preparation was suspended in an organ bath containing Krebs bicarbonate solution for isometric tension recording. Decrease of bath temperature from 37°C to 20°C (cooling) had no effect on basal tone,but markedly augmented the contractile responses to cholinergic nerve stimulation (0.5Hz) and ACh (3×10-6 M). The potentiation of ACh-induced contraction was also obtained in the presence of physostigmine (10-7M) or tetrodotoxin (5×10-7M). Cooling caused a parallel shift to the left of the dose -response curve of ACh. At 37°C and 20°C, the doses of ACh required to produce 50% of maximum response were 17.6+3.5 and 3.5±0.4μM, respectively. However, the affinity of the muscarinic receptors determined from pA2 values for the competitive antagonist atropine was significantly smaller at 20°C than at 37°C. On the other hand, ACh-induced contraction of the trachea incubated with isotonic KCl solution or with Ca-free EGTA (0.1mM) solution was increased at 20°C. From these observations, it is concluded that increased responsiveness of the rat tracheal muscle to ACh at lower temperature is mainly due to an acceleration of Ca release from intracellular stored site.

Preparation of uniform haemoglobin free human erythrocyte ghosts in isotonic solution

A method is described for the preparation of haemoglobin free human erythrocyte ghosts in isotonic solutions using dielectric breakdown technique. In this single haemolytic procedure, almost complete removal of haemoglobin (⩽ 0.1%) was achieved by subjecting the erythrocytes suspended in phosphate buffered, isotonic KCl solution at 0°C to three consecutive electrical field pulses of 16 kV/cm in the presence of 10 mM EDTA; EDTA was used to prevent electrical haemolysis. Haemolysis is induced by subsequent dilution with isotonic and isoionic solution to lower the EDTA concentration. Haemolysis is complete after 5 min; the cells are centrifuged, washed and resuspended in a solution of the same composition and osmolarity containing 4 mM MgCl 2, but no EDTA. The resealing process, carried out at 37°C, was complete in about 1 h. Measurements of the size distribution of the ghost cells in the hydrodynamically focusing Coulter Counter at varying field strengths in the orifice revealed that the ghost population is nearly uniform. The mean (modal) volume of the ghost cells was 110–120 μ m 3 when suspended in phosphate buffered NaCl solution. The apparent breakdown voltage was about 1.3 V.

Potassium inactivation in single myelinated nerve fibres of Xenopus laevis.

1. Voltage clamp measurements were performed on single myelinated nerve fibres of the frog Xenopus laevis. 2. During long-lasting depolarizations the potassium current decayed in a fast phase with a time constant of about 0.6 sec and a following slow phase with a time constant between 3.6 (V=0) and 20 sec (V=100 mV). 3. The decay of the potassium current was the result of an inactivation of the potassium permeability and not of a shift of the potassium equilibrium potential as shown by experiments in isotonic KCl solution. 4. At a hyperpolarization of −20 mV the potassium inactivation was fully removed. It remained incomplete even at large depolarizations. The steady-state inactivation curve was S-shaped but not symmetrical. 5. The experimental results could be described by extending the Hodgkin-Huxley equations introducing two terms of potassium inactivation.

Glutamate release from the retina during spreading depression.

AbstractThe retina was charged with 14C labled glutamate in a near isotonic KCl solution containing, in addition to the label, 25 mM unlabeled glutamate. In extracts of retinas thus charged most of the label was present as glutamate, an appreciable amount as glutamine, and some as aspartate, γ‐aminobutyric acid and other, probably non‐aminated, metabolites of glutamate.The charged retinas, superfused in a chamber, were stimulated either chemically with unlabeled glutamate or KCl solutions, or electrically with direct current. These stimuli caused a transient increase in the transparency of the retina, indicative of spreading depression. Only minute portions of the superfusion solution were collected, and subjected to paper electrophoresis. The radioactivity of the labeled spots was determined with a strip counter. When not stimulated the retina released mostly glutamine, but during and after the various modes of stimulation the release of glutamate increased markedly. Repeated stimulation with short current pulses did not cause a transparency increase and did not enhance the glutamate release. During spontaneous spreading depressions a slight increase in glutamate release was observed. The possibility that glutamate release is the primary mechanism in spreading depression is discussed.

Tetrodotoxin and manganese ions: effects on electrical activity and tension in taenia coli of guinea pig.

Tetrodotoxin, at concentrations up to 5 x 10(-6) gram per milliliter, has no effect on the spontaneous discharge in the smooth muscle of taenia coli. However, the spontaneous discharge is abolished by Mn(++) at a concentration of 0.5 millimole per liter. The contraction induced by immersing the muscle in isotonic KCl solution is also suppressed in the presence of Mn(++). Because Mn(++) is a specific suppressor of the spike induced by Ca(++) and tetrodotoxin is an inhibitor of the spike induced by Na(+), we suggest that Ca(++) is a charge carrier in the production of spike potential in the smooth muscle and that the entry of intervening Ca(++) through the membrane acts as a trigger for the contraction of smooth muscle.

Injury Induced in Isolated Muscle Fiber by Locally Applied Ultrasound

A muscle fiber was sonated by means of a needle machined into the tip of a steel acoustic horn. During sonation of a fiber in Ringer solution, there is a breakdown of cross striations in the region close to the needle tip and a movement of sarcoplasm toward this injured region. At cessation of sonation, the movement of sarcoplasm towards the injured region ceases and reverses direction: striation breakdown proceeds along the length of the fiber. Sonation does not evoke injury or sarcoplasmic movement when a fiber is immersed in paraffin oil, calcium-free Ringer, or in isotonic solutions of KCl, NaCl, or Na oxalate. If any one of these solutions is replaced by unbuffered Ringer, or if calcium ion is added to any one of these solutions, movement and injury can be evoked. Sarcoplasmic movement and injury occur in CaCl2 solutions as dilute as 0.001 M. This response to ultrasound appears to be calcium-ion-dependent. Apparently sonation increases membrane permeability to calcium ion. [Work supported by the National Institutes of Health, U. S. Department of Health, Education, and Welfare.]

Na, K, Ca, and Mg ion action on coronary vascular resistance in the dog heart.

Local effects of major cations on coronary vascular resistance were studied in the beating dog heart. This was accomplished by shunting the blood around the heart and lungs, clamping the arch of the aorta and perfusing arterial blood at a constant rate into the ascending aorta. Perfusion pressure was measured during intracoronary infusion of isotonic solutions of NaCl, KCl, CaCl2, MgCl2, and MgSO4 and hypertonic solutions of NaCl and KCl at rates which raised cation concentrations in coronary blood without significantly affecting concentrations generally within the body. Coronary vascular resistance decreased as a function of the infusion rate of isotonic solutions of KCl, MgCl2, and MgSO4 and increased as a function of the infusion rate of an isotonic solution of CaCl2. Isotonic NaCl had no effect. Resistance changes occurred before measurable change in the proportion of a minute spent in electrical systole by the ventricle. These findings, together with those previously reported for the dog foreleg, suggest that the coronary vascular bed is actively dilated by localized slight increase in plasma concentration of K or Mg and actively constricted by localized slight increase in plasma concentration of Ca.

The behavior of isolated hearts of the grasshopper, Chortophaga viridifasciata, and the moth, Samia walkeri, in solutions with different concentrations of sodium, potassium, calcium, and magnesium.

1. The blood of Chortophaga viridifasciata was analyzed. The average concentrations of inorganic cations expressed as milligrams per cent are: sodium, 250.66; potassium, 13.52; calcium, 11.40; and magnesium, 51.15. The osmotic pressure of the blood at 0 degrees C. is 10.7 atmospheres. Protein and non-protein nitrogen, expressed as milligrams per cent, are 253.4 and 140.0, respectively. 2. The blood of Samia walkeri has an osmotic pressure of 13.36 atmospheres at 0 degrees C. Its protein nitrogen is 628.58, and its non-protein nitrogen, 441.20 milligrams per cent. 3. The effects of isotonic chloride solutions of sodium, potassium, calcium, and magnesium and of distilled water on the heart beat of these two species were determined. The heart of the grasshopper failed to beat in isotonic solutions of KCl, MgCl(2), or in distilled water. For both insects, sodium was found to be the least toxic ion. In the case of the grasshopper, calcium ranks next in order. In the case of the moth, potassium ranks next after sodium and is followed by calcium and magnesium. 4. The ratio of sodium to potassium in milligrams per cent, necessary for maintaining the normal heart beat of Chortophaga viridifasciata is 3 to 1, but it may be increased to at least 34 to 1 without any appreciable effects. The ratio of potassium to calcium necessary for maintaining the normal heart beat of this insect is 1 to 1, and may be increased to as much as 3 to 1. 5. The ratio of sodium to potassium, in milligrams per cent, necessary for maintaining the normal heart beat of Samia walkeri was found to be equal to or to exceed 1 to 13.8. The sodium content may be increased so that the ratio of sodium to potassium is 34 to 1 without any toxic effects. The ratios of potassium to calcium required for normal heart beat in this insect may be 1 to 1, 2 to 1, or 3 to 1. 6. The hearts of the grasshoppers beat normally in isotonic solutions having an osmotic pressure of 10.7 atmospheres. They beat equally well in solutions having an osmotic pressure of 13.4 atmospheres. The hearts of the cynthia pupae beat normally in isotonic solutions having an osmotic pressure of 13.36 atmospheres. However, they also beat normally in solutions having an osmotic pressure of 10.02 atmospheres. Therefore, although the blood of the cynthia moth and of the grasshopper have different osmotic pressures, their hearts are tolerant to solutions having the same tonicity. Because of this, and since the ratios of potassium to calcium necessary for maintaining normal heart beats of both insects are the same, solutions favorable to the grasshopper may also be favorable to the cynthia moth.

The Potassium Absorption by Pigeon Blood Cells.: A Considerable Potassium Absorption by Pigeon‐ and Hen Blood Cells in Observed when a Hypertonic Sodium Chlorided Solution is Added

Summary.It is shown that freshlv drawn pigeon blood when placed at body temperature during the first hour will absorb half or more of the plasma potassium. Later the plasma potassium concentration will increase. Lack of oxygen will stop the potassium absorption and instead potassium of the cells is lost. and sodium increased.Addition of isotonic KCl solution will not change the potassium absorption.But if you besides KCl add a hypertonic solution of NaCl a considerable potassium uptake is seen, and it will carry on for more than three hours. In this way the cell potassium concentration can be augmented by more than 20 %.Blood from hen or cock will not absorb potassium unless a hypertonio NaCl solution is added.The hypertonic solution may increase the active potassium absorption or it may tighten the cell membrane so that the loss of potassiiini from the cells is decreased. The second possibility is considered the most probable. The theory is strengthened by an experiment where 1 % ethyl alcohol produced a loss of potassium, whereas simultaneous addition of hypertonic NaCl solution produced a considerable potassium uptake. Simultaneously with the potassium absorption an increase of the haematocrit values is seen.The find solution of the problem may be given by experiments with radioactive potassium.The experiments correspond to similar experiments made with bacillus coli communis (Ørskov 1948).