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At least 19 recordsLinked to original sources
PubMed1977

Effect of salt solutions on radiosensitivity of mammalian cells. III. Treatment with hypertonic solutions.

V79 Chinese hamster cells were treated with hypertonic solutions of NaCl or KCl and irradiated rat various times before, during, or after exposure to the solution. In solutions of molarities between 0-2 and 0-5 M, the cellular radiosensitivity increases with the molarity of the bathing solution. At these molarities, the hypertonic solution need not be present during irradiation to sensitize cells. Furthermore, radiosensitivity of cells could be increased by exposing cells for longer times to the hypertonic solution before irradiation. At higher salt concentrations (at 1-5 to 1-8 M), significant radioprotection is observed. Survival curve data showed that this protection was characterized by an increase in DO and a decrease in n, while the survival curves of cells sensitized with 0-465 M NaCl or with lower concentrations exhibited mainly changes in DO. The 1-55 M NaCl solution must be present during radiation to give a protective effect. Prolonged exposure to the salt before irradiation reduced the amount of radioprotection afforded by the salt. The results are discussed in terms of the effects of ions on histones, cellular water structure and the cell-aging cycle.

Cell Survival↗
PubMed1977

Increase in human intestinal permeability following ingestion of hypertonic solutions.

1. A simple oral loading technique involving the ingestion of solutions containing lactulose is described. Timed urinary excretion of lactulose, which is non-metabolizable, is used as an indicator of intestinal permeability, and measured by quantitative paper chromatography. 2. This technique has been used to investigate the intestinal permeability of apparently healthy adults following the ingestion of solutions made hypertonic by the addition of the solutes sucrose, glucose, mannitol, glycerol, urea and sodium chloride. 3. These experiments show that intestinal permeability to lactulose increases as the solute concentration in the ingested solution is increased. Susceptibility to this effect, though consistent for each individual, shows considerable variation between subjects. 4. Factors thought to be pernitent to the enhancement of intestinal permeability by hypertonic solutions, and some possible implications of this, are discussed.

Disaccharides↗
PubMed1978

The sarcoplasmic reticulum and T-system of rat extensor digitorum longus muscles exposed to hypertonic solutions.

Excised rat extensor digitorum longus muscles were soaked in a Krebs solution made hypertonic with extra NaCl and fixed using a combination of acrolein and glutaraldehyde dissolved in the same hypertonic Krebs. Electron microscopic examination showed that the sarcoplasmic reticulum (S.R.) of these muscles occupied the same fraction of fibre volume as it did in control muscles soaked and fixed in normal Krebs solution, contradicting previous studies on frog muscle. It appears unlikely that the S.R. is the rapidly exchanging Na+-compartment of rat muscle which enlarges in hypertonic solutions, or that it is an extracellular compartment. The T-system of hypertonic muscles was swollen, but its volume is insufficient to form the rapidly exchanging Na+-compartment.

Animals↗
PubMed1978

T-tubule swelling in hypertonic solutions: a freeze substitution study.

Striated muscles from Rana pipiens have been exposed for variable periods of time to Ringer solutions made hypertonic by addition of either sucrose or sodium chloride. The muscles have been rapid-frozen and then prepared for electron microscopy by either freeze-substitution, freeze-fracture or cryoultramicrotomy. The only compartment greatly affected by hypertonicity is the transverse tubular system, which is visibly swollen. None of the elements of the sarcoplasmic reticulum increase in size.

Animals↗
PubMed1977

Inhibition by hypertonic solutions of Ca-dependent electrogenesis in single crab muscle fibers.

This study describes the effect of hypertonic solutions on isolated muscle fibers of Callinectes danae. Solutions of twice normal tonicity (2.0 T) inhibit both the normal graded membrane responses and the spikes induced by procaine, tetraethylammonium, or barium. The inhibition is maintained throughout exposure to hypertonic solutions prepared by addition of impermeant solutes such as NaCl, sucrose, or Tris-propionate, but is reversible on their withdrawal. In the presence of permeant solutes such as glycerol or acetamide, the inhibition is transient. In both cases the onset of inhibition of the depolarizing Ca electrogenesis is correlated with shrinkage of the fiber. In the case of permeant solutes, the time course of recovery of the graded responses or the spikes follows the recovery of the fiber volume. Changes in the passive electrical characteristics of the fibers due to hypertonic solutions were unrelated to the blockade of membrane Ca activation. The current-voltage relationship in hypertonic sollution revealed no increase in depolarizing K activation. Inhibition of the graded membrane responses and spikes appears to be associated with depression of Ca conductance. Hypertonic solutions might affect the activation of Ca conductance through reduction of the electric field generated by fixed negative surface charges and/or morphological changes in the T tubules. Membrane depolarization elicited little or no tension in 2.0 T solutions while caffeine contracture (10 mM) with an ampliture of 76% of the maximal contractile ability could still be elicited. This indicates that direct effects of hypertonic solutions on the contractile apparatus were not responsible for loss of tension. The latter is attributed to the inhibition of the transmembrane Ca currents.

Acetamides↗
PubMed1979

Antiulcer activity of hypertonic solutions in the rat: possible role of prostaglandins.

The effects of hypertonic solutions on gastric acidity and on experimental gastric and duodenal ulcers as well as on gastric prostaglandins (PGs) were studied in the rat. The oral administration of a 10% NaCl solution resulted in complete absence of free acidity and very significant reductions in total acidity 24 h after pyloric ligation. The antiulcer effect of hypertonic saline was studied in three experimental models. In pyloric-ligated rats, both the incidence and the severity of gastric ulcers were remarkably reduced by hypertonic saline treatment. Indomethacin-induced gastric erosions were significantly reduced by hypertonic NaCl or sorbitol and completely prevented by hypertonic xylitol. Cysteamine-induced duodenal ulcers were also significantly reduced by hypertonic solutions of NaCl, xylitol or sorbitol. In the latter model, indomethacin potentiated the ulcerogenic effect of cysteamine and also reduced the efficacy of the hypertonic NaCl gavage. The possible contribution of PGs to these effects was further investigated by analysing PGE in the gastric mucosa and juice. Rats treated orally with hypertonic NaCl solutions had several-fold higher PGE contents in their gastric mucosa as well as higher PGE levels in the gastric juice. It is concluded that hypertonic solutions stimulate endogenous PGE biosynthesis and also exert profound antiulcer effects in the rat. A causal relationship between the two phenomena is suggested.

Animals↗
PubMed1979

Some effects of hypertonic solution on the properties of spontaneous transmitter release in the hypogastric ganglia of guinea-pigs.

1. The effects of hypertonic solutions on spontaneous transmitter release at synapses in the hypogastric ganglia of guinea-pigs were studied using intracellular recording techniques. 2. Hypertonic solutions were found to cause a marked hyperpolarization of the ganglion cells and this was accompanied by an increase in both the threshold and input resistance of these cells. 3. The frequency of spontaneous quantal release was found to depend exponentially on the tonicity of the bathing solution with a 50% increase in tonicity producing a 7-9 fold increase in the frequency of release. 4. Hypertonic solutions were also found to increase the degree of bursting within the spontaneous process so that the proportion of multiquantal spontaneous potentials was found to be increased in such solutions. 5. Two different models, the 'charge-screening' model (Van der Kloot & Kita, 1973) and the 'Ca-increase' model (Shimoni, Alnaes & Rahamimoff, 1977), for the mechanism underlying the effects of hypertonic solution were considered.

Action Potentials↗
PubMed1976

Mechanism of inhibition of gastric acid secretion by hypertonic solutions and vasopressin.

An experiment was performed in female rats in order to assess the influence and mechanism underlying the effects of hyperglycemia, hypertonic saline and vasopressin upon the gastric acid secretion and mucosal blood flow (MBF). Infusion of isotonic saline did not alter acid output and gastric clearance of plasma aminopyrine whereas hypertonic solutions (20% glucose or 3% NaCl) significantly increased plasma osmolality and decreased the acid secretion within 30 min and recovered to normal levels after 2 h. Vasopressin also effectively inhibited acid secretion. Both hypertonic solutions and vasopressin decreased the mucosal blood flow. However, the ratio (R) of MBF to gastric secretory rate which is a helpful guide to the mechanism of secretory inhibition did not significantly change in either case. We concluded that all three agents probably had a direct action on secretion rather than decreasing MBF. The mechanism of inhabition of acid secretion and its relationship to MBF was suggested and discussed.

Animals↗
PubMed1979

Excitation of squid giant axons in hypotonic and hypertonic solutions.

Excitability of intracellularly perfused squid giant axons was maintained in hypotonic solutions (down to 300 mOSM) and in hypertonic solutions (up to about 10 OSM), when osmolalities of internal and external solutions were adjusted to be equal with glycerol, glucose, or sucrose. Molar concentrations of ions were kept constant during one series of experiments. The resting potential and the amplitude of the action potential did not change in both hypotonic and hypertonic solutions. With reduction of osmolality, the duration of action potential decreased and the maximum rate of rise and conduction velocity increased. By raising osmolality, the duration was prolonged and the maximum rate of rise and the conduction velocity decreased. Effects of osmolality change were almost reversible. However, these effects were not directly related to the osmolality change but seemed to be related to the viscosity change of the solutions. When the osmolality of external solution was raised with NaCl (up to 2.6 M NaCl), the overshoot increased in porportion to the logarithm of the NaCl concentration. The slope of increase was about 50 mV/decade. However, the resting potential showed little change. With increase of the NaCl concentration, the duration of the action potential increased.

Animals↗
PubMed1975

[The effect of hypertonic solutions on contracture of a tonic muscle fiber].

Effect of glycerol, sucrose and NaC1 hypertonic solutions exerted on potassium contracture and resting membrane potential in isolated frog tonic muscle fibres were studied. Sucrose and NaC1 hypertonic solutions induce a stable depolarization and depress potassium contracture, while glycerol results in a transient depolarization followed by recovery of resting membrane potential and contracture reactions. The removal of 400 mM glycerol induces an insignificant depolarization and disappearance of contracture reactions, however, after the removal of sucrose of NaC1 hypertonicity both the parameters tend to restore. The isolated phasic and tonic fibres lose irreversibly potassium contracture reactions after the removal of 100 mM and 400 mM glycerol, respectively, the latter being more resistant to this procedure. Nevertheless it is concluded that the T-system is equally important for excitation--contraction coupling in tonic and in phasic fibres.

Animals↗
PubMed1978

The effect of hypertonic solutions on the rate of relaxation of contracture tension in Mytilus smooth muscle.

1. The effect of the bathing solution tonicity on the mechanical properties of the anterior byssal retractor muscle (ABRM) of Mytilus edulis was examined. 2. The rate of relaxation of contracture tension produced by acetylcholine (ACh) was greatly reduced when the bathing solution tonicity was increased by adding NaCl, KCl or LiCl after the removal of ACh, whereas a decreased tonicity increased the rate of relaxation. 3. The contracted ABRM in hypertonic solutions showed no active shortening after an isotonic release and barely redeveloped active tension after a quick release. 4. The resistance to stretch increased with increasing tonicity of the bathing solution. 5. The wet weight of the ABRM decreased much more markedly in sucrose-hypertonic solution than in Na-, K- or Li-hypertonic solutions, but the decrease in the rate of relaxation was less marked in the former, indicating that there may be little relation between the rate of relaxation and the degree of osmotic deformation of the ABRM fibres. 6. It is suggested that the elevated ionic strength in the myoplasm may be related to a reduction in the rate of detachment of the cross-linkages between the thick and thin filaments.

Animals↗
PubMed1975

Coagulation changes during second-trimester abortion induced by intra-amniotic prostaglandin E2 and hypertonic solutions.

The coagulation system was studied in twenty-seven patients undergoing second-trimester abortion induced by intra-amniotic prostaglandin (P.G.) E2 alone and in combination with a hypertonic solution of urea or glucose. Changes consistent with intravascular coagulation, namely a rise in fibrin degradation products and a fall in plasma-fibrinogen and platelet-count, were observed in those patients treated using P.G.E2 with hypertonic urea. Similar but less pronounced changes were found in the group treated using P.G.E2 with hypertonic glucose. In patients treated with P.G.E2 alone no changes suggestive of intravascular coagulation were detected. One patient treated using P.G.E2 with hypertonic urea who did not abort for 26 hours demonstrated changes indicative of a pronounced degree of disseminated intravascular coagulation. These findings show that when abortion is induced using P.G.E2 and a hypertonic solution, particularly hypertonic urea, disseminated intravascular coagulation can occur as a result of a hypertonic agent being used.

Abortion, Induced↗
PubMed1977

Volume changes in sarcoplasmic reticulum of rat hearts perfused with hypertonic solutions.

To explore whether morphometry of intracellular membrane-limited subcompartments can be used to follow physiological volume changes in such subcompartments in hearts rapidly fixed by perfusion fixation, we have measured osmotically induced volume changes in electron micrographs of longitudinally oriented sarcoplasmic reticulum (LSR) and terminal cisterns (TC) of rat left ventricular myocardial cells. Vascular perfusion with solutions whose osmolality varied from 0.67 to 1.88 isomolal showed that in the hyperosmolal range LSR volume decreased linearly. Approximately 79% of LSR luminal volume participated in the osmotic rey unresponsive. By contrast, we found that the TC responded by dilation when hearts were perfused with hypersomolal NaCl, NaI, LiCl, or sucrose. Furthermore, with hyperosmolal NaCl the dilation developed within 1 minute; its rate and extent of development were concentration-dependent; it manifested an obligate association with prior or concomitant T-tubular dilation and was not readily reversible. We conclude that (1) the technique sensitively measures in situ changes of LSR volume; (2) most of LSR luminal water is osmotically responsive, but a significant fraction may not be; (3) exposure to hyperosomolal solutions may bring about (perhaps irreversible) structural changes in the diadic membrane complex, leading to changes in its solute permeability.

Animals↗
PubMed1976

[The effect of hypertonic solutions on the electrical activity of isolated frog muscle spindles].

Electrical activity of an isolated frog muscle spindle was investigated in hypertonic solutions obtained by adding 400 mM of sucrose, glucose or glycerine to the Ringer solution. In sucrose and glucose hypermedia the frequency of background impulse activity first increased and then decreased up to zero; receptor potentials and evoked impulse activity simultaneously decreased and disappeared. In the glycerine hypermedia impulse activity after some increase returned to normal and then a second rise of frequency to a constant supernormal level was observed. After returning to the Ringer solution from sucrose or glucose the background and evoked impulse activity progressively returned to normal. But after glycerine hypermedia a significant growth in the background impulse activity and a small change in frequency of evoked impulse activity were observed. The observed changes of electrical activity of the muscle spindle in hypermedia are discussed in terms of deformation of sensory endings and intrafusal muscles fibres leading to depolarization of the receptor membrane.

Animals↗
PubMedDate not supplied

[Changes induced by hypertonic solutions in the transportation of calcium by the cardiac reticular sarcoplasma].

In the sarcoplasmic reticulum of the myocardium, celular organell which function is to regulate the cytoplasmic concentration of calcium in contraction and relaxation, we have studied the effect of hypertonic solutions of sucrose between 1 and 6.96 times the normal tonicity in order to observe the behavior of the internal linked or free calcium of this structure, as well as to prove the hypothesis that hypertonic solutions encourage the calcium exit of the sarcoplasmatic reticulum with the resulting signs of contractures. The following results were obtained: 1. The ATP hydrolisis and calcium transport rate are 14% and 90% respectively of the maximum speeds of 10(-5) M in calcium, while for concentrations of 10(-7) M or ess of the said cation, the transport rates and the ATPase do not reach 5% of the maximum values. 2. Between 1 and 2.54 times of the normal tonicity the calcium uptake remains between 400 and 500 nmoles of calcium/mg protein/min, the transported amount of calcium varies between 14 and 16 nmoles/mg protein and the rate of the ATP hydrolysis increases a 37% to 0.4 M in sucrose. 3. Between 0.4 and 1.2 M in sucrose of 2.54 to 6.96 times the isotonicity, the calcium transport rate velocity as well as the ATP hydrolisis are strongly inhibited. The vesicles volume minimizes and the amount of linked calcium remains within the control values, proving that the capacity of linking this cathion is independent from sarcoplasmic reticulum volume. These results show that the sarcoplasmic reticulum is involved in the contractures induced by hypertonic solutions in intact cells, since the osmolarity increase produces changes of volume which results in a decrease of the calcium transportation velocity or in an increase of the exit of said cathion.

Animals↗
PubMedDate not supplied

Release of oxytocin and substance P-like peptides from the rat posterior pituitary lobe incubated in situ after infusion of hypertonic solution into the third cerebral ventricle.

Release of oxytocin and Substance P-like peptides from the rat posterior pituitary lobe incubated in situ after infusion of hypertonic solution into the third cerebral ventricle. Acta Physiol. Pol., 1978, 29 (1): 9-16. The experiments were carried out on male rats. Under general urethane and chloralose anaesthesia the ventral surface of the hypothalamus and the pituitary gland were exposed by a transpharyngeal approach and the anterior pituitary lobe was entirely removed. The posterior lobe with the remaining neural and partially vascular connections with the hypothalamus was incubated in situ. Oxytocin and Substance P-like peptides were assayed biologically in six 20-min samples of the fluid outflow from the posterior pituitary lobe incubated in situ. At the beginning of collection of the fourth sample a hypertonic solution was infused into the third ventricle through a micropipette. This infusion increased significantly the release of oxytocin and insignificantly that of Substance P-like pepides from the posterior pituitary lobe into the incubation fluid.

Animals↗
PubMed1975

Effect of bulbar perfusion with acid, hypertonic solutions, and acetylcholine on gastric acid secretion in dogs.

Dogs were provided with innervated pouches of the fundic stomach and the duodenal bulb. One dog also had an isolated pouch of the distal duodenum. Acid secretion was stimulated by intravenous infusion of a low dose of pentagastrin (ICI 50 123). Bulbar pouches were perfused with solutions of 0.9% Na C1, 0.1 N HC1, 40% glucose, 40% NaC1, and 40% peptone or with 0.1% solutions of acetylcholine chloride. Acidification of the bulbar pouches profoundly inhibited the acid output from the gastric ppoches. Perfusion with acetylcholine produced a transient inhibition of acid secretion. When hypertonic solutions were perfused through the bulbar pouches or the pouch of distal duodenum, no inhibition occurred. It is concluded that hypertonic solutions are not activators of the bulbar inhibitory mechanism that has been shown to respond to reduction of the intrabulbar pH. Inhibition following bulbar perfusion with acetylcholine may mean that liberation of the hypothetical humoral agent, bulbogastrone, to some extent is under cholinergic control.

Acetylcholine↗
PubMedDate not supplied

Substance P-like peptides and vasopressin release from posterior pituitary lobe incubated in situ after intracarotid injections of hypertonic solution in rats.

The experiments were performed on male rats, drinking 2% NaCl solution ad libitum for 12 days instead of tap water. The pituitary gland was exposed by the transpharyngeal approach under urethane-chloralose anaesthesia. The posterior lobe remained in neural and partial vascular connection with the hypothalamus, whereas the anterior lobe was entirely removed. Samples of the outflow medium from the incubated in situ rat posterior pituitary lobe were collected during 30 min intervals. Substance P-like peptides and vasopressin activities were assayed by the biological tests. Injections of hypertonic solution into the internal carotid artery did not change vasopressin release, but induced an increase in Substance P release from the posterior pituitary lobe into the incubation medium. Under conditions of unexcitability of the osmosensitive cells, triggering vasopressin release, the injection of hypertonic solution into the internal carotid artery stimulated the Substance P-like peptides release from the posterior pituitary lobe.

Animals↗