Hyperosmotic NaCl Research Articles

The influence of central hyperosmotic solutions on drinking and vasopressin release following peripheral hyperosmotic NaCl in the minipig

The drinking and lysine vasopressin (LVP, porcine vasopressin) responses were measured in minipigs given simultaneous intracarotid (i.c.) (1.28 ml/min) and intracerebroventricular (i.c.v.) (50 μl/min) infusions of solutions of differing osmolality and sodium content. Observations were made during, and for a further 15 min after, the combined infusions which lasted 15 min. Drinking in response to i.c. infusion of 2.0 Osm NaCl started with a latency of 7 min and was unaffected by simultaneous i.c.v. infusion of 0.15 M NaCl, was additive with the drinking produced by i.c.v. 1.4 Osm NaCl, sucrose or mannitol, and inhibited by i.c.v. infusion of 1.4 Osm urea. LVP release following i.c. hyperosmotic NaCl was observed as early as the first blood sample, at 2 min, and was attenuated by i.c.v. hyperosmotic urea and attenuated, then slightly augmented, by i.c.v. infusions of the hyperosmotic non-electrolyte solutions. These results show that drinking following peripheral administration of an osmotic stimulus in the minipig can add to that induced by central infusions of solutions that of the cerebrospinal fluid (CSF) but may have increased or decreased CSF sodium concentration. By contrast, the stimulated LVP release was attenuated by solutions that decreased CSF sodium concentration. Thus, in minipigs, separate osmoreceptors appear to mediate osmotically induced drinking and LVP release.

Determination of solute reflection coefficients in kidney brush-border membrane vesicles by light scattering: influence of the refractive index

Solute reflection coefficients σ of cell membrane vesicles or liposomes are commonly determined by comparison of the water flow induced by a gradient of the studied solute and that of a reference molecule using light scattering techniques. However, variations in scattered light which are mainly related to change in vesicle volume are also influenced by the refractive index of the surrounding medium. Therefore comparing kinetics of vesicle shrinkage induced by hyperosmotic solutions which have different refractive indexes might lead to an under or over estimation of σ. We determined σ NaCl in rat kidney brush-border membrane vesicles by two different approaches using mannitol, a poorly permeant molecule, as reference. (1) The refractive index of the hyperosmotic NaCl solution was adjusted to that of mannitol by addition of polyvinyl pyrrolidone ( M r 40 000), without a significant increase in osmolality. Thereby the change in scattered light intensity induced by osmotic vesicle shrinkage due to gradients of NaCl and mannitol were comparable and led to a σ NaCl value close to one instead of the previously published value of 0.53. (2) The reflection coefficient was calculated from the lifetime of vesicle shrinkage which is not refractive index-dependent. Again σ NaCl was not different from one. These results suggest that the water proteic pathways found in the luminal membrane of proximal tubules are not shared by salts.

Intracellular and luminal ion concentrations in sea turtle salt glands determined by x-ray microanalysis

The lachrymal salt glands of hatchlings of the green sea turtle (Chelonia mydas) secrete a hyperosmotic (up to 2000 mosmol·kg−1) NaCl solution. X-ray microanalysis of frozen-hydrated glands showed that during secretion intracellular Na+ concentration in the principal cells increased from 13 to 34 mmol·l−1 of cell water, whilst Cl− and K+ concentrations remained unchanged at 81 mmol·l−1 and 160–174 mmol·l−1, respectively. The high Cl− concentration and the change in Na+ concentration are consistent with the prevailing paradigm for secretion by the structurally and functionally similar elasmobranch rectal gland. Concentrations of Na+, Cl− and K+ in the lumina of secretory tubules of secreting (Na+ 122, Cl− 167, K+ 38 mmol·l−1) and non-secreting (Na+ 114, Cl−1 174, K+ 44 mmol·l−1) glands were similar and the fluid was calculated to be approximately isosmotic with blood. In the central canals Na+ and Cl− concentrations were similar but K+ concentration was lower (11–15 mmol·l−1). It is concluded that either a high transepithelial NaCl gradient in secretory tubules and central canals is very rapidly dissipated during the short time between gland excision and freezing, or that ductal modification of an initial isosmotic secretion occurs.

Effect of Water Balance on Thermoregulation in Waterproof Frogs (ChiromantisandPhyllomedusa)

Arboreal frogs of the genera Chiromantis and Phyllomedusa generally have low evaporative water loss (EWL) but can regulate water loss to maintain body temperature (Tb) at about 40 C at high ambient temperatures (Ta). Thermoregulatory responses of these animals were tested in a thermal gradient and in a wind tunnel to determine whether these responses were affected by the water balance of the animal Hydrated frogs maintained higher Tb in the thermal gradient and frequently employed physiological thermoregulation (enhanced EWL) rather than move away from the heat source. When deprived of water they maintained lower Tb and rarely employed evaporative cooling. When subjected to high Ta in a wind tunnel, regulated Tb was significantly lower (and EWL correspondingly higher) in animals having water reserves in their bladders. Infusion of water into frogs initially lacking bladder reserves decreased Tb and increased EWL in both species. Infusion of hyperosmotic NaCl into hydrated animals increased Tb and reduced EWL markedly in Chiromantis but resulted in only a slight rise in Tb in Phyllomedusa. These frogs resemble other thermoregulating vertebrates in that both behavioral and physiological responses to heat are influenced by hydration state with the result that water is conserved when in short supply.

Resistance of mammalian red blood cells of different size to hypertonic milieu

1. 1. The resistance of different mammalian red blood cells (RBCs) to hyperosmotic environments was studied. RBCs of six mammalian species were exposed to 10 increasingly hyperosmotic NaCl solutions for 24 hr at 5°C. 2. 2. The osmolality at which the amount of liberated haemoglobin reached a preset level (e.g. 3–4% of the total haemoglobin) showed a linear correlation with negative slope with RBC volume. This indicates that small RBCs are more resistant to hyperosmotic milieu than large ones. 3. 3. A similar relation can be found from literature data when maximal urinary tonicities are plotted as a function of RBC volume, i.e. animals with the ability to produce highly concentrated urine have small RBCs. 4. 4. RBC volume and maximal urinary tonicity in mammals are therefore tightly linked. Future research will have to show whether this correlation is fortuitous or not and whether, as can be speculated, RBC size is directly or indirectly regulated by the kidney.

Are ninhydrin-positive substances volume-regulatory osmolytes in rat renal papillary cells?

1. A study has been made of the concentrations and contents of ninhydrin-positive substances (n.p.s.), presumed to be predominantly but not exclusively amino acids, in the cells of rat renal papillary slices incubated in variously modified Krebs phosphate-bicarbonate Ringer solution. 2. When the medium osmolality was increased from 710 (control) to 2000 mosmol/kg H2O by additional NaCl and urea, the steady-state cellular n.p.s. concentration rose from 42.3 +/- 0.6 (mean +/- S.E. of mean; n = 36) to 105 +/- 2 (n = 68) mmol/l (glycine equivalent). Cell fluid content fell from 5.11 +/- 0.09 (n = 36) to 4.16 +/- 0.11 (n = 68) microliter/mg solute-free dry weight. Hence cell n.p.s. content increased from 211 +/- 4 (n = 36) to 421 +/- 10 (n = 68) nmol/mg solute-free dry weight. 3. A comparable loss of cell fluid was observed when urea was replaced by sucrose or sorbitol. No increase in cell n.p.s. occurred, and there was a marked cell Na+-for-K+ exchange. 4. The extent of the increase in cell n.p.s. in the presence of 2000 mosmol/kg H2O (NaCl + urea) was sensitive to the presence of external anions in the sequence acetate less than Cl- less than NO3- less than or equal to SCN-. 5. Cell n.p.s. concentration increased progressively as the medium osmolality was increased by the addition of urea, but Na+ at a concentration above 330 mmol/l had an inhibitory effect. The increase in n.p.s. concentration was also significantly reduced in hyperosmotic media in which Na+ was replaced by choline. 6. The increase in cell n.p.s. content due to hyperosmotic NaCl + urea was completely inhibited by pre-incubation in control medium containing trimethylamine N-oxide. 7. On transference of slices from control to hyperosmotic media (NaCl + urea) the steady-state increase in cell n.p.s. concentration was complete within 20 min and followed a time course similar to that for cell fluid loss. The n.p.s. concentration and cell fluid content returned to control levels, with similar time courses, following re-immersion in control medium. 8. Efflux of alpha-amino[1-14C]isobutyric acid (AIB) from slices pre-loaded in control medium containing 1 mmol AIB/l was slightly but significantly slower into AIB-free hyperosmotic NaCl + urea than into AIB-free control medium. The rate of efflux was greatly increased by the presence of hyperosmotic sucrose or very high Na+ (935 mmol/l).(ABSTRACT TRUNCATED AT 400 WORDS)

Phrenic afferents and their role in inspiratory control.

In anesthetized cats, with vagi cut and the spinal cord severed at the C8 level, phrenic motor and/or sensory discharge was recorded. Small afferent phrenic fibers were identified through their activation by lactic acid, hyperosmotic NaCl solution, or phenyl diguanide. They exhibited a spontaneous but irregular low-frequency discharge. Block of their conduction by procaine had no effect on eupneic motor phrenic activity. Large afferent phrenic fibers showed a spontaneous rhythmic discharge, and cold block (6 degrees C) of these fibers significantly prolonged the phrenic discharge time (Tphr) and total breath duration (TT) during eupnea. The stimulation of all afferent phrenic fibers lowered the impulse frequency of phrenic motoneurons (f impulses) and shortened both Tphr and TT. When the stimulation was performed during cold block all of the effects on phrenic output persisted, but changes in timing were less pronounced. Under procaine block, only the effects of phrenic nerve stimulation on Tphr persisted. These results suggest that both large and small afferent phrenic fibers control the inspiratory activity with a prominent role of small fibers on phrenic motoneuron impulse frequency.

Effect of acute and chronic cardiac denervation on osmotic release of vasotocin in chickens.

Hypo- and hyperosmotic NaCl were infused intravenously to examine osmotic release of arginine vasotocin (AVT) in anesthetized, acutely cardiac-denervated chickens and in conscious, chronically denervated birds. Mean arterial blood pressure was consistently higher in denervated compared to sham-operated chickens but heart rates were similar in experimental and control groups. Plasma AVT concentrations (pAVT) were significantly higher than controls in acutely, but not chronically, denervated chickens. The slope of the regression line relating pAVT to plasma sodium concentration was higher in denervated birds indicating that removal of cardiac receptor activity increases the osmotic sensitivity of the AVT system. The results suggest that cardiac end-net receptor activity may participate in the regulation of blood pressure and can modulate the release of antidiuretic hormone in the chicken.

Behavioral Thermoregulation during Dehydration and Osmotic Loading of the Desert Iguana

Dehydration to 80% initial body weight had no effect on the skin and core temperatures at which desert iguanas exited the hot or cold side of an electronic shuttle box. Hyperosmotic NaCl loading resulted in a significant decrease in the upper threshold skin temperature (44.23 ± 0.07 to 43.82 ± 0.08 C) and both the lower threshold skin (37.52 ± 0.16 to 34.93 ± 0.20 C) and core (39.28 ± 0.10 to 37.05 ± 0.25 C) temperatures. Hypoosmotic NaCl loading resulted in a significantly higher upper threshold skin temperature (42.84 ± 0.09 to 43.44 ± 0.08 C) but significant decreases in lower threshold skin (34.93 ± 0.11 to 32.11 ± 0.14 C) and core (35.34 ± 0.11 to 33.97 ± 0.14 C) temperatures. While changes in thermoregulatory behavior can be correlated with changes in plasma osmolality, shifts in the lower behavioral threshold during osmotic manipulation may be due to ionic rather than osmotic influences.

The identity of the current carriers in canine lingual epithelium in vitro

Ion transport across the lingual epithelium has been implicated as an early event in gustatory transduction. The fluxes of isotopically labelled Na + and Cl − were measured across isolated canine dorsal lingual epithelium under short-circuit conditions. The epithelium actively absorbs Na + and to a lesser extent actively secretes Cl −. Under symmetrical conditions with Krebs-Henseleit buffer on both sides, (1) Na + absorption accounts for 46% of the short-circuit current ( I sc ); (2) there are two transcellular Na + pathways, one amiloride-sensitive and one amiloride-insensitive; (3) ouabain, added to the serosal solution, inhibits both I sc and active Na + absorption. When hyperosmotic (0.25 M) NaCl is placed in the mucosal bath, both I sc and Na + absorption increase; net Na + absorption is at least as much as I sc . Ion substitution studies indicate that the tissue may transport a variety of larger ions, though not as effectively as Na + and Cl −. Thus we have shown that the lingual epithelium, like other epithelia of the gastrointestinal tract, actively transports ions. However, it is unusual both in its response to hyperosmotic solutions and in the variety of ions that support a transepithelial short-circuit current. Since sodium ion transport under hyperosmotic conditions has been shown to correlate well with the gustatory neural response, the variety of ions transported may likewise indicate a wider role for transport in taste transduction.

Tonicity of carotid blood influences salt gland secretion in pekin duck

In 23 male and female, salt adapted Pekin ducks, both carotids were chronically cannulated. At defined states of threshold and subthreshold conditions and of steady secretion of the salt glands, comparative intracarotid (i.c.) and intravenous (i.v.) infusions for 2–15 min were made with hyperosmotic (1,000 mosm·kg−1) and isosmotic (300 mosm·kg−1) NaCl and mannitol solutions and with hyposmotic (200 mosm·kg−1) glucose solution. At steady salt gland secretion, 2 ml/2 min hyperosmotic NaCl further stimulated the salt glands, the response being slightly more rapid with i.c. than with i.v. infusion. The salt glands also responded, although more weakly, to 2 ml/2 min hyperosmotic mannitol. At threshold and subthreshold conditions, 4 ml/2–4 min of hypertonic NaCl activated the salt glands more rapidly when infused i.c. than when infused i.v. A steady salt gland secretion was rapidly and strongly inhibited by i.c. infusion of 2 ml/2 min and 15 ml/15 min hyposmotic glucose; the effects of the same infusions i.v. were weak and delayed. Fifteen ml/15 min of isosmotic NaCl activated the salt glands, the response being initially greater to i.c. than to i.v. infusion. Fifteen ml/15 min isosmotic mannitol given i.c. caused transient salt gland inhibition followed by activation; i.v. infusion produced a delayed activation. We conclude that receptive elements in the carotid vascular bed, possibly in the brain, are sensitive to tonicity changes and take part in salt gland control. The receptors may be primarily sodium sensitive. The nonlinearity of their influence on salt gland activity, namely slight, temporary activation but strong, sustained inhibition, may be due to nonlinear characteristics of either the stimulus-response coupling mechanisms of the sodium sensitive cephalic receptor, or of the central integration of the cephalic osmoreceptor signal with other, extracerebral signals originating from volume and/or osmosensitve vagal afferents.

Estimation of whole-body capillary transport parameters from osmotic transient data.

A mathematical model has been developed of short-term, extrarenal, whole-body fluid volume regulation. The Kedem and Katchalsky equations are used to describe rapid movements of crystalloid and colloid solutes and water between five fluid compartments. Simulation results showing rapid cell volume changes following a hyperosmotic crystalloid infusion demonstrated the necessity of considering the effect of cellular water shifts in osmotic transient experiments. From measurements of plasma volume and osmolality in acutely nephrectomized dogs subjected to isosmotic and hyperosmotic NaCl infusions and with the model, six parameters related to capillary membrane transport of water and NaCl were estimated. The mean capillary filtration capacity from six experiments was estimated as 0.01 ml.min-1.mmHg-1.100 g-1 of dog. This increased about threefold due to the hyperosmolality. Mean values of capillary diffusion capacity and osmotic reflection coefficient for NaCl were 0.37 cm3.s-1.100 g-1 and 0.087, respectively. These results support the use of the osmotic transient approach and a mathematical model to study the role of microvascular transport in whole-body fluid volume regulation.

Hyperosmotic NaCl and severe hemorrhagic shock: role of the innervated lung.

Infusions of hyperosmotic NaCl (2,400 mosmol/l; 4 ml/kg) were given to dogs in severe hemorrhagic hypotension by intravenous injection (72 expts) or intra-aortic injection (25 expts). In 46 experiments intravenous infusions were given during bilateral blockage of the cervical vagal trunks (local anesthesia or cooling). Intravenous infusions (without vagal blockade) restore arterial pressure, cardiac output, and acid-base equilibrium to normal and cause mesenteric flow to overshoot prehemorrhage levels by 50%. These effects are stable, and indefinite survival was observed in every case. Intra-aortic infusions of hyperosmotic NaCl produce only a transient recovery of arterial pressure and cardiac output but no long-term survival. Intravenous infusions with vagal blockage produce only a transient recovery of cardiac output, with non long-term survival. Measurement of pulmonary artery blood osmolarity during and after the infusions shows that a different pattern is observed in each of these three groups and strongly indicates that the first passage of hyperosmotic blood through the pulmonary circulation at a time when vagal conduction is unimpaired is essential for the production of the full hemodynamic-metabolic response, which is needed for indefinite survival.

Hyperosmotic NaCl and severe hemorrhagic shock

Intravenous infusions of highly concentrated NaCl (2,400 mosmol/l; infused volume 4 ml/kg; equivalent to 10% of shed blood), given to lightly anesthetized dogs in severe hemorrhagic shock, rapidly restore blood pressure and acid base equilibrium toward normality. No appreciable plasma volume expansion occurs for at least 12 h, indicating that fluid shift into the vascular bed plays no essential role in this response. Initial effects wee sustained indefinitely; long term survival was 100%, compared to 0% for a similar group of controls treated with saline. Hemodynamic analysis of the effects of hyperosmotic NaCl showed that these infusions substantially increase mean and pulse arterial pressure, cardiac output and mesenteric flow, whereas heart rate was slightly diminished. These effects immediately follow infusions with no tendency to dissipate with time (6-h observation). We conclude that hyperosmotic NaCl infusions increase the dynamic efficiency of the circulatory system, enabling it to adequately handle oxygen supply and metabolite clearance, despite a critical reduction of blood volume.

Regulation of body volume by salivation in a tick challenged with fluid loads.

Injection into the hemolymph of 1.2% NaCl, 11.2% sucrose, 2.3% urea (all approximately isosmotic to hemolymph), or distilled water induced salivary fluid secretion in the ixodid tick Amblyomma hebraeum Koch. Saline gave the largest response at high doses. Injection of hyperosmotic NaCL into the hemolymph did not induce salivation but led to the drinking of distilled water in amounts sufficient to dilute the salt load to isosmolarity. Atropine only partially inhibited salivation induced by NaCl, sucrose, and distilled water. Reserpine markedly inhibited salivation induced by NaCl. We propose that at least two sensory pathways (one cholinergic, one not) converge on the secretory nerve. The physiological significance of the cholinergic pathway is not known. The other pathway probably mediates the regulation of hemolymph volume, possibly via stretch receptors, but its transmitter is not known.

Ontogeny of lateral preoptic unit activity in rats

Extracellular single unit recordings were made from units within the lateral preoptic area (LPO) of infant rats from 1 day of age through 31 days of age (postweaning). The rats were anesthetized with dial-urethane and basal (spontaneous) spike rates were recorded for 10–20 min. The rats also received pain-arousal stimulation (tail-pinch and sc injection of formalin solution), and osmotic stimulation (sc or ip injection of hyperosmotic NaCl or sucrose solutions). LPO units were spontaneously active in neonatal rats; however, basal spike rates increased during development. Also increasing during development was the percentage of LPO units which displayed alteration of spike rate in response to hyperosmotic injections (osmosensitive). However, LPO units were found that were responsive to severe pain-arousal stimulation at all ages tested. The developmental changes in LPO unit activity characteristics paralleled the morphological development of LPO neurons and the development of osmotically induced drinking behaviors.

Do Frogs Drink?

ABSTRACT Drinking in response to dehydration and exposure to saline solutions was measured in adult Rana pipiens, Bufo marinus and Xenopus laevis, and tadpoles of Rana catesbeiana. These animals normally occupy quite different types of environments where the possible advantages of drinking may differ. Small amounts of the external media were swallowed by all the animals and the quantity usually increased when they were placed in hyperosmotic NaCl solution. However, no relationship between the oral intake of water and the particular conditions, such as the degree of dehydration, was observed. Usually 80–90% of the total water uptake occurred by absorption across the skin. Thus although ‘secondary’ type drinking takes place, ‘primary’ drinking did not appear to occur. These results directly confirm the general popular impression that amphibians, in contrast to other tetrapods and marine teleosts, do not drink in order to rehydrate.

Osmosensitivity of rat third ventricle and interactions with angiotensin

Injections of hyperosmotic solutions (1- to 5-microliter injections of NaCl or sucrose solutions ranging in osmolarity from 0.34 to 0.90 osmol/l) into the anteroventral third ventricle (AV3V) of rats resulted in short latency drinking antidiuretic, and pressor responses. AV3V injections or infusions of combined angiotensin-hyperosmotic NaCl solution did not result in drinking greater than the sum of drinking to angiotensin and hyperosmotic NaCl separately administered. Differences in water versus saline drinking fluid preferences provided a behavioral dissociation of angiotensin and hyperosmotic sensitive neural mechanisms. Comparison of AV3V and lateral preoptic injection sites provided an additional separation since angiotensin was equally effective at both sites whereas osmotic stimulation was more effective at the AV3V site. AV3V lesions have previously been reported to abolish drinking, antidiuretic, and pressor responses to angiotensin and hyperosmotic stimulation. The data reported here provide additional evidence that angiotensin and hyperosmotic stimuli may both act on tissue surrounding AV3V but suggest that the neural substrates for these stimuli are not identical.

Influence of red cell shape on surface charge topography

Human red blood cells (RBCs), transformed from discocytes into crenated shapes by incubation in hyperosmotic NaCl, have increased rates of agglutination in the presence of either poly- l-lysine (PLL) or soybean agglutinin (SBA). Reversion to discocytes by resuspension in isoosmotic NaCl lowers agglutination rates back to normal levels. Crenation also causes a reversible decrease in the binding of cationized ferritin (CF) particles/μm 2 of RBC surface area and focal clustering of CF particles. The decrease in CF binding and focal CF clustering are probably due to a rearrangement of negative charge bearing molecules such as glycoproteins on the RBC surface. Clustering of membrane glycoproteins may also account for the increased agglutination rates with PLL and SBA. These observations support the hypothesis that integral membrane proteins which bear negative charges and receptors at the RBC surface are associated with a cytoskeleton within the red cell. Distortion of the RBC cytoskeleton may induce a redistribution of integral membrane proteins and thus modify the surface properties of the cell.

Osmotic stimulation of pepsin secretion in the rat

The effect of the osmolarity of intragastric instillates on pepsin secretion was studied in rats anaesthetised with urethane. Irrigation of the stomach with solutions of sucrose and NaCl, resp. caused a concentration-dependent increase in pepsin output. A stimulation was observed already by hypotonic solutions and the maximal effect was obtained by 300 m-osmole/l of sucrose and by 600 m-osmole/l of NaCl (13- and 10-fold stimulation resp.). A similar time course in the increase of pepsin output was produced by hyperosmotic solutions (600 m-osmole/l) of sucrose, urea, NaCl and choline chloride. Pepsin output was stimulated maximally within 30 min and decreased thereafter, but remained at about 4--6-fold higher levels than during the previous irrigation with distilled water. Replacement of hyperosmotic instillates by distilled water reduced pepsin secretion to the initial level. Hypertonic ethanol (600 m-osmole/l) increased pepsin output only slightly. Vagotomy, pretreatment with atropine (1 mg/kg i.v.) or cimetidine (5 mg/kg i.v.), local anesthesia of the gastric mucosa with 4% lidocaine or intravenous infusion of PGE2 (2 microgram/kg X min) did not antagonise the stimulation of pepsin output induced by hyperosmotic NaCl (600 m-osmole/l). The results indicate that the increase of the osmolarity of intragastric instillates stimulates pepsin secretion in the rat without involvement of neural (vagal or local cholinergic reflexes) or hormonal mechanisms (release of gastrin) which are known to stimulate gastric secretion in the gastric phase.