Injection Of CaCl2 Research Articles

Influence of insulin on sodium efflux in barnacle muscle fibers.

The efflux of radiosodium in single muscle fibers from the barnacleBalanus nubilus was irresponsive to internal or external application of insulin. However, this was not the case with fibers isolated from a barnacle specimen pre-exposed overnight to a large dose of insulin. External application of insulin to pre-exposed fibers caused a decrease in the rate of decline of the radiosodium efflux and stopped the decline in the fractional rate constant for Na efflux. Such kinetics were interpreted as indicating that insulin acts either by releasing sequestered Na or abolishing the process of sequestration. Internal application of saline slowed the rate of decline but failed to completely abolish the mechanism of sequestration. Only in the presence of insulin was the fractional loss of Na each second constant. Internal application of insulin caused a prompt step-up in the rate of Na efflux, followed by a reduced efflux rate constant. This meant that injected insulin caused the release of sequestered Na, leading to partial saturation of the efflux. The response of the Na efflux to injected denatured insulin, though resembling that to native insulin was much smaller in size. Internal application of lysozyme produced a transitory step-up in the rate of Na efflux but failed to produce the kinetics observed with native or denatured insulin. Overnight exposure of the barnacle to a dose of denatured insulin failed to render the fiber sensitive to external and internal application of denatured or native insulinin vitro. Experiments with ouabain-poisoned fibers showed that external or internal application of native insulin caused stimulation of the remaining Na efflux. They also showed that a 10-fold increase in the concentration of ouabain failed to further reduce the ouabaininsensitive Na efflux. Microinjection of GTP into ouabain-poisoned fibers pre-exposed to insulin resulted in a striking rise in the remaining Na efflux. The magnitude of this effect was considerably greater than that in unexposed fibers. The response which was dose-dependent could be blunted by prior injection of CaCl2. Similarly, the response to CaCl2 injection could be blunted by prior injection of GTP. The evidence brought forward is compatible with the view that insulin acts by abolishing the mechanism of internal Na sequestration and by increasing the activity of the guanylate cyclase system.

Cardiac Purkinje fibres

The influence of intracellular calcium concentration [Ca2+]i on the steady state membrane currents i infinity was studied in a range of clamp potentials between -20 and -100 mV. Injection of CaCl2 or Ca-EGTA (pCa less than or equal to 6) increased i infinity whereas injection of K-EGTA diminished it. The changes delta i infinity were attributed to a change in steady state potassium conductance, gK infinity, by four arguments: delta i infinity was restricted to potentials negative to -20 mV and depended on clamp potential in an inward rectifying manner. delta i infinity displayed a reversal potential, Erev' which followed log [K+]o with 60 mV for a tenfold change. Since Erev obtained during Ca injection agreed with Erev observed during EGTA injection the potassium driving force had to be constant. When gK was blocked by superfusion with 20 mM Cesium neither CaCl2 nor K-EGTA injection modified i infinity.

Cardiac Purkinje fibres

The pacemaker tail current of sheep Purkinje fibres became larger when CaCl2 was injected intracellularly by pressure, whereas it was reduced or even abolished by injection of K-EGTA. The analysis of the [Ca2+]k-induced changes in the steady state activation (s infinity) curve suggested that the effect could not be explained on the basis of internal screening of surface charges. The position of the s infinity-curve on the potential axis remained almost unchanged after the injection of CaCl2 or K-EGTA. On the other hand, the vertical amplitude of the s infinity-curve on the current axis, proportional to gK2, was enlarged during CaCl2 injections and strongly diminished by K-EGTA injections. Ca injection displaced the fully deactivated part of the s infinity-curve to larger outward current which corresponds to an increase in gK1. EGTA injection reduced gI1. The results correspond to a [Ca2+]i-sensitive potassium permeability. A possible interpretation is that [Ca2+]i controls Ca-binding near the inner mouth of a potassium channel and that the binding is followed by a change in the channel's configuration from a closed to an open state.

Cardiac Purkinje fibres

CaCl2, K-EGTA or Ca-EGTA were injected into shortened Purkinje fibres in order to modify the concentration of ionized calcium ([Ca2+]i). Two injection techniques were used: A method of microiontophoresis between two intracellular microelectrodes and a method of pressure injection using heating in a closed system. Continuous microiontophoresis of CaCl2 at a rate of 10−13 Mol/s, caused shortening of the action potential, enhancement of the afterpotential, and hyperpolarisation of the resting potential within 1 s. This response was steady within about 10 s and disappeared in less than 1 s when injection was ended. Pressure injection of small volumes of 1 M CaCl2 evoked the same response. Injection of KCl was ineffective. When K-EGTA was injected the action potential became longer and the afterpotential was suppressed. After 2 min of continuous injection the fibres depolarized to about −40 mV. The effect of K-EGTA injection was fully reversible but recovery required several minutes. Injection of Ca-EGTA buffer solutions evoked (initially) a response similar to that described for CaCl2 injection provided that [Ca2+]i was greater than 5·10−7 M. Conversely, when [Ca2+]i was equal to or less than 1·10−7 M an EGTA-like response could be seen. The results favour (but do not prove) the idea that [Ca2+]i mediates the observed effects via an influence on the potassium conductance.

Cardiovascular depressant effects of neomycin and gentamicin in rhesus monkeys.

1. The acute cardiovascular effects of neomycin and gentamicin, representative aminoglycoside antibiotics, were examined in surgically-prepared anaesthetized rhesus monkeys. 2. Intravenous administration of 14, 28, and 56 mg/kg of neomycin consistently induced a dose-dependent depression of systemic blood pressure, cardiac output, left ventricular contractile force, maximum dF/dt of left ventricular contraction, and heart rate. Neomycin produced similar cardiovascular depressant effects when heart rate was maintained constant by electrical pacing. 3. Maximum depression of haemodynamic values usually occurred within 2 to 5 min after injection of neomycin; values then gradually returned to control levels within 20 to 30 (14 mg/kg) or 60 to 80 (56 mg/kg) minutes. 4. Injection of CaCl2 (1.35 mEq Ca2+/kg, i.v.) during the peak depressant effect of neomycin produced a rapid and maintained restoration of cardiovascular function to control levels; conversely, noradrenaline (2 mug, i.v.) of isoprenaline (0.5 mug, i.v.) produced only transient reversal of the neomycin effects. 5. Similar evidence of cardiovascular dysfunction was observed with gentamicin. 6. These findings demonstrate the direct cardiovascular depressant effects of aminoglycoside natibiotics in a higher primate species, and suggest that this adverse response is related to an alteration of calcium ion function.

The role of extracellular Ca2+ and cyclic nucleotides in the mechanism of enzyme secretion from the cat pancereas

The role of Ca2+ in protein secretion from the isolated perfused cat's pancreas, the effect of the dibutyryl analogues of cAMP and cGMP, and the interrelation of Ca2+ and the nucleotides were studied. The following results were obtained: 1. Pancreatic enzyme secretion can be elicited by CaCl2 injections into the pancreatic arteries and is linearily related to the peak Ca2+ concentration in the effluent perfusate. Different background Ca2+ concentrations in the perfusate (3 mM or 0.125 mM) do not disturb this relation, indicating that no adaptation occurs. The effect of Ca2+ injections is of the same magnitude as that evoked by the hormones pancreozymin or acetylcholine. 2. Injections of Ca2+ potentiate the effects of dibutyryl adenosine 3',5'-cyclic monophosphate (dbcAMP), dibutyryl guanosine 3',5'-cyclic monophosphate (dbcGMP) or theophylline. 3. Infusion of low doses of pancreozymin increases the Ca2+ effect. The findings indicate that extracellular Ca2+ is involved in the mechanism of enzyme secretion and that Ca2+ and cyclic nucleotides have a synergistic action on the target.

The effects of changes in arterial plasma calcium concentration on submandibular secretory potentials

1. The concentration of Ca in the arterial blood plasma perfusing submandibular glands of anaesthetized cats and possums (Trichosurus vulpecula) was altered by constant-rate close arterial injection of isotonic CaCl(2) or EDTA solutions.2. There were no significant changes in the resting potentials of surface acinar cells in either species when the arterial plasma Ca concentration was altered over the range 0-30 mM.3. Secretory potentials in response to parasympathetic stimuli and close arterial injection of ACh were reduced and finally abolished during EDTA injection, but temporarily restored by injection of CaCl(2).4. Secretory potentials in response to 1 Hz parasympathetic stimuli in the cat were enhanced by increasing the gland arterial Ca concentration up to 5 mM; but responses to 10 Hz stimuli or close arterial ACh injection were not affected. There was no such enhancement of secretory potentials in the possum.5. Increase in the gland arterial plasma Ca concentration above 5 mM caused reduction in the amplitudes of the secretory potentials to all stimuli in both species, until they were abolished at 7-10 mM in the possum and 15-20 mM in the cat.6. In both species, increase in the gland arterial plasma Ca concentration caused increase in the gland blood flow and enhancement of the vasodilator effects of parasympathetic stimuli and ACh injection. EDTA injection was sometimes associated with a vasoconstrictor response to parasympathetic stimuli.7. It is concluded that the secretory potentials, but not the resting potentials, of submandibular secretory cells require the presence of Ca in the interstitial fluid. It is suggested that Ca affects both the release of transmitter and at higher concentration the mechanism by which it activates the secretory cells.

Blood flow changes in the pituitary neural lobe of the rabbit associated with neurohypophysial hormone-releasing stimuli.

SUMMARY Blood flow rates in the posterior pituitary glands of rabbits were calculated by measuring the clearance of locally deposited 133Xe in saline detected by an externally located probe. These studies indicated that intraarterial injection of CaCl2 and central stimulation of a vagus (both hormone-releasing stimuli) caused a significant rise in blood flow, whilst during haemorrhage, also a release stimulus, the blood flow in the posterior pituitary was maintained. Pretreatment with atropine abolished the increase seen with CaCl2 and vagal stimulation and caused a significant fall in blood flow after haemorrhage. Parasympathomimetic drugs caused an increase in the flow which was also atropine-sensitive; sympathomimetic drugs and sympathetic blocking drugs caused no alteration in blood flow. These results indicate that there is a local increase in blood flow in the posterior pituitary which is associated with hormone-releasing stimuli and which is cholinergically mediated.

Parathyroid extract-induced changes in the oxidation of citrate, succinate and other organic acids by liver.

Parathyroid extract (PTE) or partially purified parathyroid hormone administered in vivo markedly altered the oxidation in vitro by rabbit liver minces of citrate, a-ketoglutarate, succinate, fumarate and lactate. With Ca++ present in the incubation medium, minces from PTE-treated animals produced more CO2 and had a greater O2 consumption than did control minces. This stimulation was due, in part at least, to a more rapid decline in metabolic activity of the control tissues. When Ca++ was absent, total metabolism was increased and the tissue derived from PTE-treated animals was less active than the control tissue. The effect was detected as early as 4 hr after injection (750 U/kg) and could be elicited with as little as 200 U (at 14 hr). The action of PTE could not be duplicated by the injection of CaCl2 into the animal. The data suggest that one effect of treatment was a general inhibition of oxidation. The stimulation of metabolism could be a consequence of this inhibition or a separate unrelated altera...

鹽化カルシウム負荷による血清カルシウム量の消長と肝臓及び腎臓との關係

鹽化カルシウム負荷による血清カルシウム量の消長と肝臓及び腎臓との關係

MICRURGICAL STUDIES IN CELL PHYSIOLOGY

By means of micro-dissection and injection Amoeba proteus was treated with the chlorides of Na, K, Ca, and Mg alone, in combination, and with variations of pH. I. The Plasmalemma. 1. NaCl weakens and disrupts the surface membrane of the ameba. Tearing the membrane accelerates the disruption which spreads rapidly from the site of the tear. KCl has no disruptive effect on the membrane but renders it adhesive. 2. MgCl(2) and CaCl(2) have no appreciable effect on the integrity of the surface membrane of the ameba when applied on the outside. No spread of disruption occurs when the membrane is torn in these salts. When these salts are introduced into the ameba they render the pellicle of the involved region rigid. II. The Internal Protoplasm. 3. Injected water either diffuses through the protoplasm or becomes localized in a hyaline blister. Large amounts when rapidly injected produce a "rushing effect". 4. HCl at pH 1.8 solidifies the internal protoplasm and at pH 2.2 causes solidification only after several successive injections. The effect of the subsequent injections may be due to the neutralization of the cell-buffers by the first injection. 5. NaCl and KCl increase the fluidity of the internal protoplasm and induce quiescence. 6. CaCl(2) and MgCl(2) to a lesser extent solidify the internal protoplasm. With CaCl(2) the solidification tends to be localized. With MgCl(2) it tends to spread. The injection of CaCl(2) accelerates movement in the regions not solidified whereas the injection of MgCl(2) induces quiescence. III. Pinching-Off Reaction. 7. A hyaline blister produced by the injection of water may be pinched off. The pinched-off blister is a liquid sphere surrounded by a pellicle. 8. Pinching off always takes place with injections of HCl when the injected region is solidified. 9. The injection of CaCl(2) usually results in the pinching off of the portion solidified. The rate of pinching off varies with the concentration of the salt. The injection of MgCl(2) does not cause pinching off. IV. Reparability of Torn Surfaces. 10. The repair of a torn surface takes place readily in distilled water. In the different salt solutions, reparability varies specifically with each salt, with the concentration of the salt, and with the extent of the tear. In NaCl and in KCl repair occurs less readily than in water. In MgCl(2) repair takes place with great difficulty. In CaCl(2) a proper estimate of the process of repair is complicated by the pinching-off phenomenon. However, CaCl(2) is the only salt found to increase the mobility of the plasmalemma, and this presumably enhances its reparability. 11. The repair of the surface is probably a function of the internal protoplasm and depends upon an interaction of the protoplasm with the surrounding medium. V. Permeability. 12. NaCl and KCl readily penetrate the ameba from the exterior. CaCl(2) and MgCl(2) do not. 13. All four salts when injected into an ameba readily diffuse through the internal protoplasm. In the case of CaCl(2) the diffusion may be arrested by the pinching-off process. VI. Toxicity. 14. NaCl and KCl are more toxic to the exterior of the cell than to the interior, and the reverse is true for CaCl(2) and MgCl(2). 15. The relative non-toxicity of injected NaCl to the interior of the ameba is not necessarily due to its diffusion outward from the cell. 16. HCl is much more toxic to the exterior of a cell than to the interior; at pH 5.5 it is toxic to the surface whereas at pH 2.5 it is not toxic to the interior. NaOH to pH 9.8 is not toxic either to the surface or to the interior. VII. Antagonism. 17. The toxic effects of NaCl and of KCl on the exterior of the cell can be antagonized by CaCl(2) and this antagonism occurs at the surface. Although the lethal effect of NaCl is thus antagonized, NaCl still penetrates but at a slower rate than if the ameba were immersed in a solution of this salt alone. 18. NaCl and HCl are mutually antagonistic in the interior of the ameba. No antagonism between the salts and HCl was found on the exterior of the ameba. No antagonism between the salts and NaOH was found on the interior or exterior of the ameba. 19. The pinching-off phenomenon can be antagonized by NaCl or by KCl, and the rate of the retardation of the pinching-off process varies with the concentration of the antagonizing salt. 20. The prevention of repair of a torn membrane by toxic solutions of NaCl or KCl can be antagonized by CaCl(2). These experiments show directly the marked difference between the interior and the exterior of the cell in their behavior toward the chlorides of Na, K, Ca, and Mg.