scholarly journals Partitioning of Acid-Base Regulation Between Renal and Extrarenal Sites in the Adult, Terrestrial Stage of the Salamander Ambystoma Tigrinum During Respiratory Acidosis

1991 ◽  
Vol 157 (1) ◽  
pp. 47-62 ◽  
Author(s):  
DANIEL F. STIFFLER
Keyword(s):  
Renal Involvement ◽  
Electrical Potential ◽  
Respiratory Acidosis ◽  
Ambystoma Tigrinum ◽  
Electrical Potential Difference ◽  
Acid Base ◽  
Total Ammonia ◽  
Unidirectional Fluxes ◽  
Na Uptake ◽  
Partial Compensation

Adult Ambystoma tigrinum were cannulated non-occlusively in the truncus arteriosus and subjected to 24 h of hypercapnia in 3% CO2. Adults showed the typical compensatory pattern, shared by larvae and many other amphibians, of partial compensation (44%) for the induced respiratory acidosis. Adults whose urinary bladders were ligated to allow the urine to bypass the bladder compensated as well as shams, indicating that the urinary bladder of this species is not necessary for compensation. Radioisotopic measurements of net and unidirectional fluxes of Na+ or Cl− in whole animals showed no effects of hypercapnia. Partitioning of acid-base responses showed that 75–80 % of the regulation takes place across the skin. The rest is accomplished by the kidneys. This did not change during hypercapnia and there was no evidence of renal involvement in the compensation. Total ammonia (NH3+NH4+) comprised only about one-sixth of the total cutaneous acid excretion. The charge associated with the cutaneous excretion of H+ equivalents was balanced by both Na+ uptake and Cl− loss. In contrast to larvae, whose cutaneous electrical potential difference (PD) increases during hypercapnia, adults decrease their PD. This could mean that acidosis stimulates an electrogenic H+ secretion and/sor that cutaneous Na+ and Cl− permeabilities change. Both possibilities are consistent with the data.

Evidence of active regulation of cerebrospinal fluid acid-base balance

1981 ◽  
Vol 51 (2) ◽  
pp. 369-375 ◽  
Author(s):  
S. W. Bledsoe ◽  
D. Y. Eng ◽  
T. F. Hornbein
Keyword(s):  
Cerebrospinal Fluid ◽  
Electrical Potential ◽  
Respiratory Acidosis ◽  
Respiratory Alkalosis ◽  
Electrical Potential Difference ◽  
Passive Transport ◽  
Acid Base Balance ◽  
Acid Base ◽  
Transport Control ◽  
Base Balance

To test the passive transport hypothesis of cerebrospinal fluid (CSF) [H+] regulation, we altered the relationship between plasma [H+] and the electrical potential difference between CSF and blood (PD) by elevating plasma [K+] during 6-h systemic acid-base disturbances. In five groups of pentobarbital-anesthetized dogs, we increased plasma [K+] from 3.5 to an average of 7.8 meq/l. Hyperkalemia produced an increase in the PD of 6.3 mV by 6 h with normal plasma acid-base status (pHa 7.4), of 8.3 mV with isocapnic metabolic acidosis (pHa 7.2), of 5.3 mV with isocapnic metabolic alkalosis (pHa 7.6), of 9.2 mV with isobicarbonate respiratory acidosis (PaCO2 61 Torr) and of 5.7 mV with isobicarbonate respiratory alkalosis (PaCO2 25 Torr). The change in CSF [H+] at 6 h in each group was the same as that observed in normokalemic animals (Am. J. Physiol. 228: 1134-1154, 1975). This result is not consistent with the passive transport hypothesis. The CSF-blood PD is therefore not an important determinant of CSF [H+] CSF [H+] homeostasis must result from some form of active transport control.

Effect Of Environmental Water Salinity on Acid-Base Regulation During Environmental Hypercapnia in the Rainbow Trout (Oncorhynchus Mykiss)

1991 ◽  
Vol 158 (1) ◽  
pp. 1-18 ◽  
Author(s):  
GEORGE K. IWAMA ◽  
NORBERT HEISLER
Keyword(s):  
Rainbow Trout ◽  
Respiratory Acidosis ◽  
Environmental Water ◽  
Ammonia Concentration ◽  
Acid Base ◽  
Clear Trend ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Exchange Processes ◽  
Total Ammonia ◽  
Time Courses

Acid-base regulation in rainbow trout acclimated to about 3, 100 and 500 mmol l−1 Na+ and Cl−, at constant water [HCO3−], was assessed during 24h of exposure to 1% CO2 and during recovery. The respiratory acidosis induced by a rise in plasma PCOCO2 to about 1.15kPa (8.5mmHg, 3mmol l−1), 1.33kPa (10mmHg, 100 mmol l−1) or 1.5 kPa (11.2 mmHg, 500 mmol l−1) was partially compensated for by accumulation of plasma HCO3−. The degree of pH compensation depended on the salinity of the environmental water, being about 61, 82 and 88% at 3, 100 and 300 mmol l−1 Na+ and Cl−, respectively. [HCO3−] in animals acclimated to 100 and 500 mmol l−1 rose to higher values than that in fish at 3 mmol l−1. Plasma [Cl−] decreased during hypercapnia as compared to control concentrations in all groups of fish. Plasma [Na+] rose during the first 8 h of hypercapnia in fish acclimated to all three salinities, but recovered towards control values during the remainder of hypercapnia. The rise in plasma [HCO3−] was significantly related to the fall in plasma [Cl−], whereas the changes in plasma [Na+] were unaffected by simultaneous changes in plasma [HCO3−]. Time courses of changes in plasma [Na+] and total ammonia concentration, [Tamm], were similar but in opposite directions. The transepithelial potential (TEP) of blood relative to water was negative, close to zero and positive, averaging −21, −5.8 and +6.2 mV for fish acclimated to 3, 100 and 300 mmol l−1 Na+, respectively. After initiation of hypercapnia, which caused a quite heterogeneous response among groups, a clear trend towards depolarization was observed during the remainder of hypercapnia. These results confirm the role of active HCO3−/Cl− exchange processes for the compensation of extracellular pH during respiratory acidoses in fish.

Sodium and Water Transport Across the Jejunum of Fasted Rats

1973 ◽  
Vol 51 (6) ◽  
pp. 405-409 ◽  
Author(s):  
Ivan T. Beck ◽  
P. K. Dinda
Keyword(s):  
Sodium Transport ◽  
Fluid Transport ◽  
Electrical Potential ◽  
Electrical Potential Difference ◽  
Serosal Side ◽  
Concomitant Increase ◽  
Net Flux ◽  
Unidirectional Fluxes ◽  
Mucosal Side ◽  
Fasted Rats

The effect of 72 h fasting on the transmural electrical potential difference (P.D.), the unidirectional fluxes, and the net flux of sodium and the net transport of fluid across the jejunum of rats was investigated. Everted jejunal segments were incubated in 12 ml of Krebs–Ringer bicarbonate solution containing 5.55 mM glucose on either side for 1 h at 37 °C. Seventy-two hours fasting caused a 63% increase in the transmural P.D., a 60% increase in the flux of Na from the mucosal to the serosal side, and a 48% increase in the flux of Na from the serosal to the mucosal side. The net mucosal to serosal Na flux increased by 97%. There was also a 41% increase in fluid transport across the intestine of fasted rats. The concomitant increase in sodium and fluid transport and in transmural P.D. is consistent with the current hypotheses of fluid and sodium transport.

Acid-base-electrolyte balance responses to catecholamine antagonists in Ambystoma tigrinum

1990 ◽  
Vol 258 (6) ◽  
pp. R1363-R1370
Author(s):  
D. F. Stiffler ◽  
M. E. Kopecky ◽  
M. L. Thompson ◽  
R. G. Boutilier
Keyword(s):  
Ion Transport ◽  
High Performance ◽  
Beta Blockers ◽  
Respiratory Acidosis ◽  
Ambystoma Tigrinum ◽  
Electrolyte Balance ◽  
Adrenergic Blockade ◽  
Plasma Samples ◽  
Acid Base ◽  
Exposure Measurements

Neotenic larval Ambystoma tigrinum were subjected to hypercapnia (3% CO2, 22 Torr) for 24 h under different conditions: alpha-adrenergic blockade using phentolamine, beta-adrenergic blockade using propranolol, and sham treatments. The sham animals were able to carry out a partial extracellular pH compensation that consisted of an increase in extracellular [HCO3-]. Animals treated with catecholamine antagonists did not compensate to the same extent. Analysis of plasma samples by high-performance liquid chromatography with electrochemical detection revealed a significant increase in circulating norepinephrine, but not epinephrine, during the high-CO2 exposure. Measurements of cutaneous ion transport showed that beta-antagonists block the increased Na+ influx associated with hypercapnia, whereas alpha-antagonists inhibited the decrease in cutaneous Cl- influx that is also associated with respiratory acidosis. Additionally, both alpha- and beta-blockers inhibited the increase in transcutaneous potential difference that accompanied the respiratory acidosis. The results are consistent with a role for circulating catecholamines in compensatory ion transport responses to respiratory acidosis in this species.

OSMOTIC INHIBITION OF THE NATRIFERIC RESPONSE OF THE TOAD URINARY BLADDER TO VASOPRESSIN

1975 ◽  
Vol 67 (1) ◽  
pp. 119-125
Author(s):  
P. J. BENTLEY
Keyword(s):  
Urinary Bladder ◽  
Water Movement ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Toad Bladder ◽  
Toad Urinary Bladder ◽  
Electrical Potential Difference ◽  
Osmotic Gradient

SUMMARY The electrical potential difference and short-circuit current (scc, reflecting active transmural sodium transport) across the toad urinary bladder in vitro was unaffected by the presence of hypo-osmotic solutions bathing the mucosal (urinary) surface, providing that the transmural flow of water was small. Vasopressin increased the scc across the toad bladder (the natriferic response), but this stimulation was considerably reduced in the presence of a hypo-osmotic solution on the mucosal side, conditions under which water transfer across the membrane was also increased. This inhibition of the natriferic response did not depend on the direction of the water movement, for if the osmotic gradient was the opposite way to that which normally occurs, the response to vasopressin was still reduced. The natriferic response to cyclic AMP was also inhibited in the presence of an osmotic gradient. Aldosterone increased the scc and Na+ transport across the toad bladder but this response was not changed when an osmotic gradient was present. The physiological implications of these observations and the possible mechanisms involved are discussed.

Bicarbonate and CO2 transport across the skin of the leopard frog, Rana pipiens: effect of PGF2alpha

1997 ◽  
Vol 272 (2) ◽  
pp. R640-R647 ◽  
Author(s):  
O. A. Candia ◽  
T. Yorio
Keyword(s):  
Methodological Approach ◽  
Transport Processes ◽  
Leopard Frog ◽  
Bicarbonate Transport ◽  
Amphibian Skin ◽  
Acid Base ◽  
Reliable Determination ◽  
Net Flux ◽  
Unidirectional Fluxes

The amphibian skin represents an important organ for osmoregulation and, like the mammalian kidney, maintains acid-base balance by secreting protons or base. However, the lack of a reliable and accurate method to measure the contribution of unidirectional fluxes of HCO3- ions to this mechanism has been an obstacle for the determination of the role of bicarbonate in epithelial acid-base homeostasis. Recently, one of us developed a method that allows for the reliable determination of transepithelial fluxes of bicarbonate, and this method was applied to determine unidirectional fluxes of (14)CO2 and H(14)CO3 under a variety of conditions. We report that the combined CO2 and HCO3- mucosal-to-serosal flux under 5% CO2 was 40% larger than the opposing flux, giving a net flux in the mucosal-to-serosal direction. This net flux was inhibited by acetazolamide. In CO2-free conditions, there was no detectable net flux; however, acetazolamide and PGF(2alpha) attenuated the mucosal-to-serosal flux and established an apparent secretion of HCO3-. A model is presented that depicts twelve vectors or components to the CO2 plus HCO3- fluxes in the frog skin. This model can accurately reproduce the experimental values measured from unidirectional fluxes of CO2 and HCO3- under a variety of conditions and can explain the effects of PGF(2alpha) on unidirectional 14C-labeled fluxes as a consequence of inhibition of H+ secretion to the apical bath, similar to what was previously suggested by our laboratory using a different methodological approach. The present method, utilizing radiolabeled HCO3-, may be useful as a means to evaluate the mechanism of action of hormones and drugs that may regulate acid-base homeostasis by altering proton and bicarbonate transport processes.

Reversal of glibenclamide and voltage block of an epithelial KATP channel

1996 ◽  
Vol 271 (4) ◽  
pp. C1122-C1130 ◽  
Author(s):  
O. Mayorga-Wark ◽  
W. P. Dubinsky ◽  
S. G. Schultz
Keyword(s):  
Hydrophobic Interactions ◽  
Basolateral Membrane ◽  
Electrical Potential ◽  
Membrane Vesicles ◽  
Voltage Gating ◽  
Electrical Potential Difference ◽  
Outer Solution ◽  
Channel Inhibition ◽  
K Concentration ◽  
Voltage Gate

K+ channels present in basolateral membrane vesicles isolated from Necturus maculosa small intestinal cells and reconstituted into planar phospholipid bilayers are inhibited by MgATP and sulfonylurea derivatives, such as tolbutamide and glibenclamide, when these agents are added to the solution bathing the inner mouth of the channel. In addition, these channels possess an intrinsic "voltage gate" and are blocked when the electrical potential difference across the channel is oriented so that the inner solution is electrically positive with respect to the outer solution. We now show that increasing the concentration of permeant ions such as K+ or Rb+ in the outer solution reverses channel inhibition resulting from the addition of 50 microM glibenclamide to the inner solution and also inhibits intrinsic voltage gating; these effects are not elicited by increasing the concentrations of the relatively impermeant ions, Na+ or choline, in the outer solution. Furthermore, increasing the K+ concentration in the outer solution in the absence of glibenclamide inhibits voltage gating, and, under these conditions, the subsequent addition of glibenclamide to the inner solution is ineffective. These results are consistent with a model in which the voltage gate is an open-channel blocker whose action is directly reversed by elevating the external concentration of relatively permeant cations and where the action of glibenclamide is to stabilize the inactivated state of the channel, possibly through hydrophobic interactions.

Membranes and Membrane Processes

MRS Bulletin ◽  
1999 ◽  
Vol 24 (3) ◽  
pp. 19-22 ◽  
Author(s):  
Vasilis N. Burganos
Keyword(s):  
Membrane Separation ◽  
Transport Coefficients ◽  
Electrical Potential ◽  
Artificial Organs ◽  
Energy Storage And Conversion ◽  
Electrical Potential Difference ◽  
Catalytic Reactors ◽  
Membrane Processes ◽  
Separation Science ◽  
Structural And Functional Properties

Membrane separation science has enjoyed tremendous progress since the first synthesis of membranes almost 40 years ago, which was driven by strong technological needs and commercial expectations. As a result, the range of successful applications of membranes and membrane processes is continuously broadening. An additional change lies in the nature of membranes, which is now extended to include liquid and gaseous materials, biological or synthetic. Membranes are understood to be thin barriers between two phases through which transport can take place under the action of a driving force, typically a pressure difference and generally a chemical or electrical potential difference.An attempt at functional classification of membranes would have to include diverse categories such as gas separation, pervaporation, reverse osmosis, micro- and ultrafiltration, and biomedical separations. The dominant application of membranes is certainly the separation of mixed phases or fluids, homogeneous or heterogeneous. Separation of a mixture can be achieved if the difference in the transport coefficients of the components of interest is sufficiently large. Membranes can also be used in applications other than separation targeting: They can be employed in catalytic reactors, energy storage and conversion systems, as key components of artificial organs, as supports for electrodes, or even to control the rate of release of both useful and dangerous species.In order to meet the requirements posed by the aforementioned applications, membranes must combine several structural and functional properties.

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