Active hydrogen excretion and sodium absorption through isolated frog skin

1977 ◽  
Vol 233 (1) ◽  
pp. F46-F54 ◽  
Author(s):  
J. Ehrenfeld ◽  
F. Garcia-Romeu
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Sodium Concentration ◽  
Rana Esculenta ◽  
Open Circuit ◽  
Sodium Absorption ◽  
Ionic Balance ◽  
Proton Excretion ◽  
External Face

The in vitro skin of Rana esculenta was studied in open-circuit conditions. It was shown that when the external face is bathed in a 2-meq solution of NaCl, sodium is absorbed at a significantly higher rate than chloride. The ionic balance is maintained by excretion of hydrogen. With a mucosal solution of 2 meq Na2SO4 the equation relating sodium absorption to proton excretion is JnH+ = (-25 +/- 7) - (0.73 +/- 0.04) JnNa+. The correlation between the two variables is highly significant. Hydrogen excretion obeys saturation kinetics in relation to the sodium concentration of the mucosal solution. Maximum excretion occurs at a sodium concentration of 4 meq. When the mucosal solution is a 115-meq solution of Na2SO4 the net flux of sodium is 2.3 times higher than that of hydrogen. The balance is maintained by absorption of SO42-. The effects of various substances on the Na+ext/H+int exchange were studied. With a mucosal solution of 2 meq Na2SO4 and short-circuit conditions it was shown that the hydrogen excretion is active and nearly the same as in open circuit, the short-circuit current is equal (to within 8%) to the sum of the sodium and hydrogen net fluxes, and the correlation between the movements of the two ions is low. A model relating the active proton excretion with the sodium transport mechanism is proposed.

Prolactin effects on ion transport across cultured mouse mammary epithelium

1981 ◽  
Vol 240 (3) ◽  
pp. C110-C115 ◽  
Author(s):  
C. A. Bisbee
Keyword(s):  
Cell Cultures ◽  
Short Circuit ◽  
Collagen Gel ◽  
Mammary Epithelium ◽  
Short Circuit Current ◽  
Sodium Absorption ◽  
Collagen Gels ◽  
Mouse Mammary Epithelium

Prolactin is a known osmoregulatory hormone in lower vertebrates, and recent evidence indicates that this hormone modulates ionic concentrations in milk. In an ultrastructurally and biochemically differentiated primary cell culture system in which mouse mammary epithelium is maintained on floating collagen gels, prolactin causes an increase in short-circuit current (Isc) of monolayers of cells derived from midpregnant (24.6 to 48.0 microA . cm-2) and lactating (10.4 to 16.1 microA . cm-2) glands. Transepithelial potential differences (basal side ground) average about -12 mV and are similar to those seen in vivo. Prelactating mammary epithelial cell cultures have transepithelial resistances ranging from 374 omega . cm2 (prolactin present) to 507 omega . cm2 (prolactin absent), and lactating cell cultures have resistances averaging almost 1,000 omega . cm2. Prolactin effects require at most one day of culture maintenance in prolactin-containing medium, and the effects are not due to known contamination of prolactin preparations with arginine vasopressin or growth hormone. Medium concentrations of prolactin as low as 1 ng/ml can elicit these effects. In prelactating cell cultures not treated with prolactin, the Isc is equal to the rate of sodium absorption. Prolactin increases sodium absorption fourfold but increases Isc only twofold. Clearly, prolactin induces other active transport; neither potassium nor chloride movements can account for this additional transport. Resistance values, current-voltage plots, and permeability coefficients indicate that in vitro mammary epithelium is a moderately “tight” tissue. Comparisons with intact glands indicate that in vitro mammary epithelium closely resembles its in vivo counterpart. Floating collagen gel cultures appear suitable for elucidating transport properties in cellularly heterogeneous and structurally complex mammalian tissues.

Water and electrolyte transport by rabbit esophagus

1975 ◽  
Vol 229 (2) ◽  
pp. 438-443 ◽  
Author(s):  
DW Powell ◽  
SM Morris ◽  
DD Boyd
Keyword(s):  
Sodium Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Electrolyte Transport ◽  
Potential Difference ◽  
Sodium Absorption ◽  
Bathing Solution ◽  
Electrical Potential Difference

The nature of the transmural electrical potential difference and the characteristics of water and electrolyte transport by rabbit esophagus were determined with in vivo and in vitro studies. The potential difference of the perfused esophagus in vivo was -28 +/- 3 mV (lumen negative). In vitro the potential difference was -17.9 +/- 0.6 mV, the short-circuit current 12.9 +/- 0.6 muA/cm2, and the resistance 1,466 +/- 43 ohm-cm2. Net mucosal-to-serosal sodium transport from Ringer solution in the short-circuited esophagus in vitro accounted for 77% of the simultaneously measured short-circuit current and net serosal-to-mucosal chloride transport for 14%. Studies with bicarbonate-free, chloride-free, and bicarbonate-chloride-free solutions suggested that the net serosal-to mucosal transport of these two anions accounts for the short-circuit current not due to sodium absorption. The potential difference and short-circuit current were saturating functions of bathing solution sodium concentration and were inhibited by serosal ouabain and by amiloride. Thus active mucosal-to-serosal sodium transport is the major determinant of the potential difference and short-circuit current in this epithelium.

Regulation of amiloride-sensitive electrogenic sodium transport in the rat colon by steroid hormones

1985 ◽  
Vol 248 (1) ◽  
pp. G124-G132 ◽  
Author(s):  
P. C. Will ◽  
R. N. Cortright ◽  
R. C. DeLisle ◽  
J. G. Douglas ◽  
U. Hopfer
Keyword(s):  
Sodium Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Serum Levels ◽  
Rat Colon ◽  
Sodium Absorption ◽  
Sodium Deficiency ◽  
Synthetic Glucocorticoids

The role of steroids in the regulation of colonic sodium transport was examined by infusing steroids into adrenalectomized (ADX) rats and evaluating the short-circuit current (ISC) in vitro. Amiloride-sensitive ISC was induced by aldosterone and corticosterone with half-maximal doses (ED50) of 2 and 260 micrograms X kg-1 X h-1), respectively. Synthetic glucocorticoids such as methylprednisolone (33 mg/kg) and dexamethasone (ED50 = 30 micrograms X kg-1 X h-1) were also effective. Supramaximal doses of aldosterone (7.5 times ED50) for 24 h increased the total ISC (7-fold), the amiloride-sensitive ISC (366-fold), and the conductance (2-fold), as well as the potassium-stimulated phosphatase activity (2-fold) (reported previously). Compared with aldosterone, supramaximal doses of dexamethasone (4 times ED50) produced greater increases in the total ISC (15-fold) and the amiloride-sensitive ISC (674-fold). In contrast to aldosterone, dexamethasone also increased the amiloride-insensitive ISC (3-fold). Glucocorticoid action was not mediated by insulin since the ISC from diabetic ADX rats was increased by dexamethasone to a similar extent (11-fold) as in nondiabetic rats. Estradiol, progesterone, and testosterone did not stimulate the colonic ISC of ADX rats. The ED50 values of corticosterone and aldosterone, measured in terms of amiloride-sensitive sodium transport, produced serum levels that were slightly above those of unstressed, adrenal-intact animals and thus must be considered physiological. It is concluded that at physiological levels both steroids may mediate amiloride-sensitive sodium transport in the rat colon. However, as judged from changes in serum steroid levels, aldosterone is the physiological regulator of elevated sodium absorption in sodium deficiency.

scholarly journals Transport Properties of Locust Ileum in vitro: Effects of Cyclic Amp

1988 ◽  
Vol 137 (1) ◽  
pp. 361-385 ◽  
Author(s):  
B. Irvine ◽  
N. Audsley ◽  
R. Lechleitner ◽  
J. Meredith ◽  
B. Thomson ◽  
...  
Keyword(s):  
Cyclic Amp ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Active Absorption ◽  
Rate Of Absorption ◽  
The Difference ◽  
In Vitro Effects ◽  
Resistance Decrease

1. Short-circuited locust ilea exhibited electrical properties remarkably similar to those of recta. The large short-circuit current (Isc) and transepithelial potential, both indicating net active absorption of anions, initially began to decline to zero but could be fully restored by adding cyclic AMP or extracts of corpus cardiacum and ventral abdominal ganglia to the haemocoel side. 2. Ion substitutions and radiotracer flux studies indicated that cyclic AMP-induced ΔIsc was due to electrogenic Cl− transport with kinetics identical to those of the rectum. Concurrent decreases in transileal resistance were due to increases in both Cl− and K+ (PK) permeabilities, most evident as a resistance decrease at the apical membrane. The ΔPK was blocked by basolateral addition of Ba2+, as observed for recta. 3. Everted ileal sacs under open-circuit conditions absorbed a slightly hyperosmotic NaCl-rich fluid and the rate of absorption was increased more than twofold by cyclic AMP. This contrasts with stimulated recta which absorb primarily KCl and a hyposmotic absorbate. Flux studies with short-circuited ilea demonstrated active absorption of Na+ (JnetNa), which was stimulated twofold by cyclic AMP. Removal of external Na+ had little effect on Isc, suggesting that JnetNa involves exchange for another cation, e.g. NH4+. 4. Ilea actively secreted acid at lower rates than do recta under open-circuit conditions. Under short-circuit conditions, cyclic AMP addition led to active alkalinization of the ileal lumen at high rates, and the large Isc represented the difference between active secretion of base equivalents and net absorption of Cl−. 5. The transport capacities of locust ilea and recta are compared in relation to their ultrastructure.

Role of active potassium transport by integumentary epithelium in secretion of larval-pupal moulting fluid during silkmoth development

1975 ◽  
Vol 62 (2) ◽  
pp. 357-366
Author(s):  
A. M. Jungreis ◽  
W. R. Harvey
Keyword(s):  
Short Circuit ◽  
Flux Ratio ◽  
Short Circuit Current ◽  
Potassium Transport ◽  
Open Circuit ◽  
Ratio Test ◽  
Potassium Flux

1. The exuvial side of the pharate pupal integument is usually positive to the haemolymph-side, both in vivo and in vitro, during the period when the moulting fluid is being secreted. 2. The ratio of potassium flux toward the exuvial space is higher than that toward the haemolymph, under both open-circuit conditions and short-circuit conditions, demonstrating by the Flux Ratio test that potassium is actively transported across the isolated integument during this secretion period. 3. Just prior to ecdysis, while moulting fluid is being reabsorbed, the potassium flux ratios become unity, suggesting that active potassium transport has ceased, but the short-circuit current that remains suggests that some other ion is actively transported at this time. 4. We argue that the potassium salt solution, formed in the exuvial space (as water presumably follows the actively transported potassium), has three functions (1) to accomplish the gel--sol transformation, (2) to activate the gel enzymes and (3) to buffer the enzyme solution at a pH favourable to the activity of the gel enzymes.

Hormonal control of chloride transport across locust rectum

1978 ◽  
Vol 56 (8) ◽  
pp. 1879-1882 ◽  
Author(s):  
J. Spring ◽  
J. Hanrahan ◽  
J. Phillips
Keyword(s):  
Chloride Transport ◽  
Short Circuit ◽  
Fold Increase ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Hormonal Control ◽  
Net Flux ◽  
Hemolymph Volume ◽  
Camp Levels

Rates of ion transport across locust recta were monitored in vitro by following fluxes of 22Na+ and 36Cl−, short-circuit current (Isc), and open-circuit electropotential difference (PD) across this epithelium for several hours. Corpora cardiaca (CC) homogenates, cAMP, theophylline, and hemolymph of recently fed locusts all stimulate electrogenic transport of Cl− across locust rectum, as indicated by a two- to three-fold increase in 36Cl− net flux, Isc, and PD. Cyclic AMP caused a Cl-dependent increase in PD across the lumen-facing but not the hemocoel-facing plasma membrane of the epithelial cells. We propose that a blood-borne factor, possibly from the CC, causes an elevation in cAMP levels in rectal tissue and that this second messenger acts by increasing Cl− entry into the cell from the rectal lumen. Additional fluid absorption accompanies the resulting increase in transport of NaCl, leading to an increase in the hemolymph volume of previously dehydrated locusts.

Electrophysiological properties of guinea pig tracheal epithelium determined by cable analysis

1993 ◽  
Vol 265 (1) ◽  
pp. L38-L44
Author(s):  
T. L. Croxton
Keyword(s):  
Guinea Pig ◽  
Ion Transport ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Tracheal Epithelium ◽  
Sodium Absorption ◽  
Luminal Diameter ◽  
Cable Analysis

Electrophysiological characteristics of guinea pig tracheae were measured in vitro using an adaptation of cable analysis. This method allowed the repeated measurement of luminal diameter and epithelial electrical potential, resistance, and short-circuit current (Isc) during treatments known to affect smooth muscle contraction and epithelial ion transport. Stable values taken 3 h after mounting were as follows: diameter, 2.27 +/- 0.10 mm; potential, -28.3 +/- 2.3 mV; resistance, 327 +/- 30 omega.cm2; and Isc, 91.2 +/- 6.8 microA/cm2. These electrophysiological results are comparable to reported values for other species. However, the resistance and potential obtained in this study were larger than those previously reported for the guinea pig. Tracheal diameter was decreased 15% by methacholine and was increased 43% by subsequent isoproterenol treatment. Isoproterenol caused a small but significant increase in Isc when this quantity was normalized to tracheal length rather than to the apparent surface area. In contrast, apical amiloride decreased Isc by 51% and did not change diameter. These data validate this implementation of cable analysis, demonstrate that sodium absorption is the predominant mechanism of active ion transport by guinea pig tracheal epithelium, and indicate that this tissue has little capacity for stimulated chloride secretion.

Electrical activity and sodium transfer across in vitro pig placenta

1986 ◽  
Vol 250 (3) ◽  
pp. R474-R484 ◽  
Author(s):  
C. P. Sibley ◽  
B. S. Ward ◽  
J. D. Glazier ◽  
W. M. Moore ◽  
R. D. Boyd
Keyword(s):  
Electrical Activity ◽  
Adrenergic Receptors ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Ussing Chambers ◽  
Drug Concentrations ◽  
Voltage Clamping ◽  
Pig Placenta

Electrical activity generated by pieces of pig placenta, taken from anesthetized animals and mounted in Ussing chambers, has been investigated. Ten minutes after the start of voltage clamping, potential difference (PD; fetal side positive, open circuit), short circuit current (SCC), and resistance were 5.9 +/- 0.4 (SE) mV, 8.6 +/- 0.5 microA X cm-2, and 720 +/- 45 omega X cm2, respectively (n = 50). Ouabain (10(-4) M) added to the fetal side caused a maximum decline in PD and SCC from the time of addition of -3.7 +/- 0.98 mV and -3.9 +/- 1.4 microA X cm-2 (n = 6); epinephrine (10(-5) M) added to the fetal side caused increases of +1.0 +/- 0.2 mV and +4.0 +/- 1.4 microA X cm-2, respectively (n = 14). Drug concentrations for 50% maximum response for the effect of a series of adrenergic agonists on SCC were (in M) isoproterenol 1.2 +/- 0.05 X 10(-8), norepinephrine 6.1 +/- 0.3 X 10(-8), epinephrine 2.4 +/- 0.1 X 10(-7), and phenylephrine 4.7 +/- 0.2 X 10(-5), suggesting the involvement of fetally oriented beta-adrenergic receptors. Fetal epinephrine (10(-5) M) also stimulated net Na+ flux (Jnet) toward the fetal side to an extent equal to its effect on SCC. In control experiments Jnet was small but was inhibited by fetal side ouabain (10(-4) M) to produce a maternally directed Jnet, significantly different to the SCC. Replacement of Na+ by choline reduced SCC markedly but did not abolish it. In the absence of Na+, epinephrine had no effect on SCC. These results suggest that active Na+ transfer is not completely responsible for the control electrical activity of pig placenta. Epinephrine, however, modulates SCC entirely by stimulating net Na+ transfer toward the fetal side.

Effect of acetylcholine on Cl- and Na+ fluxes across dog tracheal epithelium in vitro

1976 ◽  
Vol 231 (5) ◽  
pp. 1546-1549 ◽  
Author(s):  
MG Marin ◽  
B Davis ◽  
JA Nadel
Keyword(s):  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Atropine Sulfate ◽  
Open Circuit ◽  
Ion Flux ◽  
Potential Difference ◽  
Tracheal Epithelium ◽  
Electrical Potential Difference

Electrical potential difference is generated across canine tracheal epithelium by active transport of Cl- toward and Na+ away from the lumen. The present study examines the effects of acetylcholine on short-circuit current, potential difference, resistance, and fluxes of 36Cl and 24Na measured across pieces of canine tracheal epithelium mounted in Ussing-type chambers. Under short-circuit conditions, acetylcholine (5 X 10(-5) M) increased significantly net ion flux toward the lumen of Cl- (n equals 7) from +1.7 +/- SE 0.5 TO +3.3 +/- SE 0.5 mueq/cm2 - h, and of Na+ (n equals 7) from -0.8 +/- SE 0.2 to +0.5 +/- SE 0.2 mueq/cm2 - h. Under open-circuit conditions, acetylcholine (5 X 10(-5) M) increased significantly the unidirectional flux of Cl- (n equals 6) toward the lumen from 4.7 +/- SE 1.3 to 5.9 +/- SE 1.4 mueq/cm2 - h, while the other measured fluxes did not change significantly, suggesting that net Cl- flux had increased toward the lumen. Atropine sulfate (10(-8) M) prevented the response to acetylcholine (5 X 10(-5) M). The increased ion flux due to acetylcholine may mediate water secretion into the airway lumen, and this secretion may have important effects on the physical properties of the liquid through which the respiratory cilia beat.

Role of calcium in the regulation of colonic secretion in the rat

1983 ◽  
Vol 244 (5) ◽  
pp. G552-G560 ◽  
Author(s):  
T. W. Zimmerman ◽  
J. W. Dobbins ◽  
H. J. Binder
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Chloride Secretion ◽  
Extracellular Calcium ◽  
Electrolyte Transport ◽  
Rat Colon ◽  
Sodium Absorption ◽  
Chloride Absorption

In vitro experiments were performed in rat colon to define the role of calcium in the regulation of electrolyte transport. Neither basal net sodium absorption (JNanet) nor JClnet was affected by varying serosal calcium from 0 to 3.0 mM, but both were decreased by 4.8 mM calcium. Removal of serosal calcium completely inhibited the effect of bethanechol, a muscarinic cholinergic agonist, which inhibits neutral sodium-chloride absorption in 1.2 mM calcium. In contrast, theophylline significantly decreased JNanet and JClnet both in the presence and absence of calcium, but the effects of theophylline were significantly less in calcium-free media. In 3.0 mM calcium bethanechol inhibited JCLnet significantly greater than JNanet and in 4.8 mM calcium bethanechol decreased JClnet equivalent to the increase in short-circuit current without significantly altering JNanet. We conclude that 1) high [Ca2+] inhibits net sodium and net chloride absorption; 2) the alteration of electrolyte transport by bethanechol is dependent on extracellular calcium, and the alteration of electrolyte transport by theophylline is not dependent on extracellular calcium but may be dependent on intracellular calcium; and 3) in addition to inhibition of neutral NaCl absorption, bethanechol stimulates chloride secretion.

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