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.

Protein kinase C potentiates cAMP-stimulated mouse duodenal mucosal bicarbonate secretion in vitro

2004 ◽  
Vol 286 (5) ◽  
pp. G814-G821 ◽  
Author(s):  
Bi-Guang Tuo ◽  
Jimmy Y. C. Chow ◽  
Kim E. Barrett ◽  
Jon I. Isenberg
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Duodenal Mucosa ◽  
Bicarbonate Secretion ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Ussing Chambers ◽  
Duodenal Bicarbonate Secretion

PKC has been shown to regulate epithelial Cl- secretion in a variety of models. However, the role of PKC in duodenal mucosal bicarbonate secretion is less clear. We aimed to investigate the role of PKC in regulation of duodenal mucosal bicarbonate secretion. Bicarbonate secretion by murine duodenal mucosa was examined in vitro in Ussing chambers using a pH-stat technique. PKC isoform expression and activity were assessed by Western blotting and in vitro kinase assays, respectively. PMA (an activator of PKC) alone had no effect on duodenal bicarbonate secretion or short-circuit current ( Isc). When PMA and dibutyryl-cAMP (db-cAMP) were added simultaneously, PMA failed to alter db-cAMP-stimulated duodenal bicarbonate secretion or Isc ( P > 0.05). However, a 1-h preincubation with PMA potentiated db-cAMP-stimulated duodenal bicarbonate secretion and Isc in a concentration-dependent manner (from 10-8 to 10-5M) ( P < 0.05). PMA preincubation had no effects on carbachol- or heat-stable toxin-stimulated bicarbonate secretion. Western blot analysis revealed that PKCα, -γ, -ϵ, -θ, -μ, and -ι/λ were expressed in murine duodenal mucosa. Ro 31–8220 (an inhibitor active against PKCϵ, -α, -β, and -γ), but not Gö 6983 (an inhibitor active against PKCα, -γ, -β, and -δ), reversed the potentiating effect of PMA on db-cAMP-stimulated bicarbonate secretion. PMA also time- and concentration-dependently increased the activity of PKCϵ, an effect that was prevented by Ro 31–8220 but not Gö 6983. These results demonstrate that activation of PKC potentiates cAMP-stimulated duodenal bicarbonate secretion, whereas it does not modify basal secretion. The effect of PKC on cAMP-stimulated bicarbonate secretion is mediated by the PKCϵ isoform.

Ion transport characteristics of the murine trachea and caecum

1992 ◽  
Vol 82 (6) ◽  
pp. 667-672 ◽  
Author(s):  
S. N. Smith ◽  
E. W. F. W. Alton ◽  
D. M. Geddes
Keyword(s):  
Cystic Fibrosis ◽  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Chloride Secretion ◽  
Open Circuit ◽  
Potential Difference ◽  
Cystic Fibrosis Gene ◽  
Tissue Type ◽  
Ussing Chambers

1. The basic defect in cystic fibrosis relates to abnormalities of ion transport in affected tissues, such as the respiratory and gastrointestinal tracts. The identification of the cystic fibrosis gene has enabled studies on the production of a cystic fibrosis transgenic mouse to be undertaken. Knowledge of normal ion transport will be necessary for the validation of any such animal model. We have therefore characterized selected responses of the murine trachea and caecum mounted in ‘mini’ Ussing chambers under open-circuit conditions. 2. Basal values for the trachea were: potential difference, 1.1 mV (sem 0.2; n=18); equivalent short-circuit current, 20.4 μA/cm2 (3.6); conductance, 18.2 mS/cm2 (1.7). Corresponding values for the caecum were: potential difference, 0.7 mV (0.1; n=18); equivalent short-circuit current, 11.0 μA/cm2 (1.6); conductance, 14.5 mS/cm2 (1.4). 3. Amiloride (10 μmol/l) produced a significant (P < 0.001) fall in potential difference of 43.0% (5.7) in the trachea, but had no significant effect in the caecum. 4. Subsequently, one of three protocols was used to assess the capacity of either tissue for chloride secretion. Addition of a combination of forskolin (1 μmol/l) and zardaverine (10 μmol/l) produced rises in the potential difference of 873% (509) in the trachea and 399% (202) in the caecum. Both A23187 (10 μmol/l) and phorbol dibutyrate (10 nmol/l) increased tracheal potential difference by 350% (182) and 147% (47), respectively. Neither had a significant effect in the caecum. 5. Subsequent addition of bumetanide caused a fall in the stimulated potential difference of between 39.8% and 71.7%, depending on secretagogue and tissue type. 6. When a homozygous transgenic cystic fibrosis mouse becomes available, these responses should allow such an animal to be distinguished from normal or heterozygous mice.

NaCl transport across equine proximal colon and the effect of endogenous prostanoids

1990 ◽  
Vol 259 (1) ◽  
pp. G62-G69 ◽  
Author(s):  
L. L. Clarke ◽  
R. A. Argenzio
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Proximal Colon ◽  
Nacl Transport ◽  
Apparent Lack ◽  
Ussing Chambers ◽  
Cl Secretion

In contrast to in vivo findings, the equine proximal colon fails to demonstrate significant net absorption of Na+ and Cl- under in vitro conditions. The present study was undertaken to determine if endogenous prostanoids are responsible for this apparent lack of ion transport. Proximal colonic tissues from ponies were preincubated in either normal Ringer solution or in Ringer containing 1 microM indomethacin and studied in Ussing chambers containing these solutions. Untreated colonic mucosa demonstrated negligible Na(+)-Cl- absorption in the basal state. In contrast, indomethacin-treated colon significantly absorbed Na+ and Cl-, primarily as the result of an equivalent increase in the mucosal-to-serosal flux of these ions. Preincubation of proximal colon in 0.1 mM ibuprofen-treated Ringer yielded similar results. Treatment of indomethacin colon with 1 mM mucosal amiloride eliminated net Na(+)-Cl- absorption without affecting the short-circuit current (Isc). The Isc in control tissue was significantly greater than in indomethacin-treated tissue and was reduced by 0.1 mM serosal furosemide. Serosal addition of 0.1 microM prostaglandin E2 or 10 mM serosal plus mucosal theophylline to indomethacin-treated tissues abolished net Na(+)-Cl- absorption and increased the Isc to levels indistinguishable from control. In contrast, control tissues were essentially unaffected by these secretagogues. These findings indicated that Na(+)-Cl- absorption in equine proximal colon was electroneutral (possibly involving Na(+)-H+ exchange) and that the tissue was capable of electrogenic Cl- secretion. However, under the in vitro conditions, basal ion transport was dominated by endogenous prostanoids that abolished Na(+)-Cl- absorption and elicited near-maximal electrogenic Cl- secretion.

In vitro studies of sodium transport across the lower intestine of a desert parrot

1980 ◽  
Vol 239 (3) ◽  
pp. R285-R290
Author(s):  
E. Skadhauge ◽  
T. J. Dawson
Keyword(s):  
Short Circuit ◽  
Electrical Potential ◽  
Flux Ratio ◽  
Short Circuit Current ◽  
Electrical Potential Difference ◽  
Na Transport ◽  
Salt Loading ◽  
Ussing Chambers ◽  
Lower Intestine

The lower intestine (coprodeum and colon) of the Australian parrot, the galah, was mounted in Ussing chambers. Short-circuit current (SCC), electrical potential difference (PD), and unidirectional fluxes of Na and Cl were measured in birds that were fed mixed seeds or were NaCl loaded. The net Na transport of both coprodeum and colon was nearly equal to the SCC, and the flux ratio for Cl was unity. In birds which received mixed seeds, average coprodeal Na transport was 7.8 mu eq . cm-2 . h-1, and PD was 19 mV. The Km for Na was 5.7 meq/l. In colon, Na transport was reduced by 67% and PD by 70%. The ratio between unidirectional Na and Cl fluxes in the serosa-mucosa direction was 0.7. Salt loading suppressed coprodeal, but increased colonic Na transport. The coprodeal and colonic SCC and NA transport of birds receiving mixed seeds were inhibited by amiloride on the mucosal side. Colonic SCC of NaCl-loaded birds was only slightly reduced by amiloride (by 17%), but stimulated by amino acids (by 18%).

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.

Components of electrogenic transport in unstimulated equine tracheal epithelium

1991 ◽  
Vol 260 (6) ◽  
pp. L510-L515 ◽  
Author(s):  
L. Joris ◽  
P. M. Quinton
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Inhibitory Effect ◽  
Open Circuit ◽  
Tracheal Mucosa ◽  
Electrogenic Transport ◽  
Ussing Chambers ◽  
Tissue Resistance ◽  
Na Substitution ◽  
Significant Underestimation

Basic components of unstimulated electrolyte transport across equine tracheal mucosa were characterized. After the tissue was mounted in Ussing chambers, both current and tissue resistance gradually increased for approximately 60 min before reaching stable values. Thereafter, under open-circuit conditions, the tissue had a resistance of 250 +/- 14 omega.cm2, generated a transepithelial potential difference of -34 +/- 1.7 (SE) mV (referenced to the serosal side) and an equivalent short-circuit current (Ieqsc) of -149 +/- 10.2 microA/cm2. Even though 10(-5) M amiloride reduced the current by approximately 65%, mucosal Na+ substitution with choline decreased the current significantly more (approximately 80%), indicating that part of the Na(+)-dependent current was amiloride insensitive. No current decrease occurred after serosal application of 10(-4) M bumetanide, which was expected to inhibit Na(+)-K(+)-2Cl(-)-mediated Cl- secretion, even though bilateral Cl- substitution with gluconate reduced Ieqsc by approximately 30 microA/cm2. Continuous short-circuit conditions caused a reversible fall in the short-circuit current that was inhibited by amiloride but not by Cl- depletion, suggesting that sustained short circuiting leads to a significant underestimation of the amiloride-sensitive Na+ transport. In the absence of Cl-, the response to amiloride was significantly smaller, which suggests that Cl- depletion also has an inhibitory effect on electrogenic, amiloride-sensitive Na+ absorption.

Effect of sulfidopeptide leukotrienes D4 and E4 on ileal ion transport in vitro in the rat and rabbit

1988 ◽  
Vol 255 (2) ◽  
pp. G175-G183 ◽  
Author(s):  
P. L. Smith ◽  
D. P. Montzka ◽  
G. P. McCafferty ◽  
M. A. Wasserman ◽  
J. D. Fondacaro
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Bathing Solution ◽  
Na Transport ◽  
Rabbit Ileum ◽  
Rat Ileum ◽  
Ussing Chambers ◽  
Meclofenamic Acid ◽  
Acid Metabolites

Effects of leukotrienes D4 and E4 (LTD4 and LTE4) on electrolyte transport were examined, employing stripped segments of rat and rabbit ileum mounted in Ussing chambers. Addition of LTD4 or LTE4 to the serosal but not the mucosal bathing solution elicited a transient increase in short-circuit current (Isc) with maximal responses seen at 10(-5) M and 10(-8) M in rat and rabbit respectively and a sustained decrease in transepithelial conductance (Gt) in the rat only. In the rat, Cl replacement, reduction of bathing solution [Ca2+] to 1 microM or pretreatment with 1 microM indomethacin or meclofenamic acid inhibited the LTD4- or LTE4-induced Isc changes with no effect on the decrease in Gt. LTD4 (10 microM) transiently increased net Cl secretion and produced a sustained decrease in both unidirectional and net Na transport and mucosal-to-serosal Cl flux in rat ileum. The decrease in unidirectional Na fluxes is accounted for predominantly by a change in the potential independent flux of Na. These results suggest that the increase in Isc in both rat and rabbit is mediated by arachidonic acid metabolites, whereas the decrease in Gt and net Na absorption in rat ileum is mediated by a cyclooxygenase-independent pathway.

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.

Sign in / Sign up

Export Citation Format

Share Document