scholarly journals The role of active transport in potassium reabsorption in the proximal convoluted tubule of the anaesthetized rat.

1997 ◽  
Vol 500 (1) ◽  
pp. 155-164 ◽  
Author(s):  
R W Wilson ◽  
M Wareing ◽  
R Green
Keyword(s):  
Active Transport ◽  
Proximal Convoluted Tubule ◽  
Anaesthetized Rat

The role of antidiuretic hormone in cold‐induced diuresis in the anaesthetized rat

1998 ◽  
Vol 162 (4) ◽  
pp. 475-480 ◽  
Author(s):  
BROMAN ◽  
KÄLLSKOG ◽  
NYGREN ◽  
WOLGAST
Keyword(s):  
Antidiuretic Hormone ◽  
Anaesthetized Rat

Evidence for electroneutral sodium chloride transport in rat proximal convoluted tubule

1986 ◽  
Vol 250 (4) ◽  
pp. F644-F648
Author(s):  
K. J. Howlin ◽  
R. J. Alpern ◽  
C. A. Berry ◽  
F. C. Rector
Keyword(s):  
Sodium Chloride ◽  
Active Transport ◽  
Sodium Transport ◽  
Chloride Transport ◽  
Proximal Convoluted Tubule ◽  
Organic Solutes ◽  
Nacl Transport ◽  
Proximal Tubular ◽  
High Chloride

One- to two-thirds of NaCl absorption in the late proximal convoluted tubule (no luminal organic solutes present) is inhibited by cyanide and thus is dependent on active transport. To examine whether this active transport-dependent NaCl transport is electrogenic or electroneutral, the effect of cyanide on transepithelial potential difference (PD) was measured in the rat proximal convoluted tubule microperfused in vivo. In the presence of an ultrafiltrate-like luminal perfusate containing glucose and alanine, cyanide addition caused the transepithelial PD to change from -0.44 +/- 0.04 to -0.05 +/- 0.03 mV (P less than 0.001). In the presence of a late proximal tubular fluid (high chloride, low bicarbonate, no organics), the transepithelial PD was 1.23 +/- 0.06 mV and was unchanged at 1.19 +/- 0.05 mV after cyanide addition (NS). To eliminate the possibility that an effect of cyanide on a putative acidification-dependent lumen-positive PD was concealing an effect on an electrogenic sodium transport-dependent lumen-negative PD, the above studies were repeated in the presence of acetazolamide. Cyanide did not affect the transepithelial PD (1.17 +/- 0.05 vs. 1.07 +/- 0.06 mV, NS). We conclude that, although cyanide-inhibitable NaCl transport is electrogenic in the presence of luminal organic solutes, it does not generate a transepithelial PD in their absence and therefore is electroneutral.

Transmembrane potentials and fluxes in isolated rabbit atria

1959 ◽  
Vol 196 (6) ◽  
pp. 1292-1296 ◽  
Author(s):  
R. L. Klein ◽  
W. C. Holland
Keyword(s):  
Action Potential ◽  
Active Transport ◽  
Terminal Phase ◽  
Transmembrane Potentials ◽  
Unidirectional Fluxes ◽  
Rabbit Atria

Data are presented from a study of transmembrane potentials and unidirectional fluxes of K42 under identical conditions in isolated rabbit atria. The effects of acetylcholine and varying extracellular concentrations of Na, K and Ca were investigated. Particular emphasis has been placed on the role of Ca and on the terminal phase of repolarization of the action potential, namely the negative after potential. Data are given which support the contention that the duration of the negative after potential depends on an active transport of K or Na, or both.

Role of ATP in respiratory control and active transport in tobacco hornworm midgut

1980 ◽  
Vol 238 (1) ◽  
pp. C10-C14 ◽  
Author(s):  
L. J. Mandel ◽  
T. G. Riddle ◽  
J. M. Storey
Keyword(s):  
Active Transport ◽  
Respiratory Control ◽  
Intermediate Form ◽  
Decay Kinetics ◽  
Kinetic Rates ◽  
Fresh Frozen ◽  
The Difference ◽  
Redox Level ◽  
K Transport

The intracellular ATP, ADP, AMP, and orthophosphate (Pi) levels were measured in the midgut of Manduca sexta. The nucleotide levels were identical in tissues either “fresh” frozen or equilibrate in regular (32 mM) K or low (8 mM) K solutions. The calculated [ATP]/[ADP][Pi]ratio was approximately 300 M-1, which is low compared to other tissues. Given the ability of this ratio to control the respiratory rate, it is speculated that this low value may cause the maximal uncontrolled respiration normally observed in the midgut. The kinetics to anoxia of active transport (Isc) and the redox level of the mitochondrial cytochromes were measured simultaneously in the midgut. The cytochromes became reduced with a time constant of 0.75 +/- 0.15 min, whereas that for Isc inhibition was 2.1 +/- 0.15 min after a delay of 0.25 min. The difference between these two kinetic rates indicates that an intermediate form of energy exists in this tissue to energize active K transport. Measurements of ATP levels during the transition to anoxia indicate that its decay kinetics are sufficiently slow for ATP to be the immediate energy source for active transport in this tissue.

Role of metabolism in K-induced tension changes in guinea pig taenia coli

1965 ◽  
Vol 208 (6) ◽  
pp. 1203-1205 ◽  
Author(s):  
M. Pfaffman ◽  
N. Urakawa ◽  
W. C. Holland
Keyword(s):  
Guinea Pig ◽  
Active Transport ◽  
Underlying Mechanism ◽  
Taenia Coli ◽  
Na Transport ◽  
Phasic Response ◽  
Metabolic Intermediates ◽  
Substrate Removal ◽  
Insight Into

Further insight into the underlying mechanism(s) of the K-induced phasic and tonic contractions of the taenia coli of the guinea pig was obtained by examining the effects of various metabolic intermediates, inhibitors of metabolism and active transport, on these responses. Evidence is presented to support the thesis that the tonic response is dependent on the aerobic breakdown of carbohydrates and is abolished by substrate removal, a decrease of temperature, DNP, lithium, and ouabain. These same factors have little or no effect on the phasic response. From the evidence presented, it is concluded that the phasic response is a passive process, whereas the tonic contracture is an active one depending on metabolism and possibly linked to active Na transport.

The Role of Surfactants in the Reversal of Active Transport Mediated by Multidrug Resistance Proteins

2003 ◽  
Vol 92 (6) ◽  
pp. 1250-1261 ◽  
Author(s):  
Katrijn Bogman ◽  
Françoise Erne-Brand ◽  
Jochem Alsenz ◽  
Jürgen Drewe
Keyword(s):  
Multidrug Resistance ◽  
Active Transport ◽  
Multidrug Resistance Proteins ◽  
Resistance Proteins

Role of thyroxine on postnatal development of ileal active bile salt transport

1986 ◽  
Vol 251 (2) ◽  
pp. G237-G242 ◽  
Author(s):  
J. E. Heubi
Keyword(s):  
Thyroid Hormone ◽  
Postnatal Development ◽  
Active Transport ◽  
Salt Transport ◽  
Maximal Velocity ◽  
Sprague Dawley ◽  
Sprague Dawley Rats ◽  
Taurocholate Transport

The role of thyroid hormone on the postnatal development of ileal active taurocholate transport uptake was measured by an in vitro incubation technique in Sprague-Dawley rats. In 16-day-old rats treated with pharmacological doses of L-thyroxine (50 micrograms X 100 g body wt-1 X day-1 on days 10-13), ileal active transport appeared precociously whose Km was 1.60 +/- 0.48 mM and Vapp (apparent maximal velocity) was 8.09 +/- 1.14 nmol X min-1 X mg dry wt-1, while age-matched shams had only passive diffusion of taurocholate. To determine whether enhanced endogenous secretion of thyroxine was capable of stimulating development of ileal active taurocholate transport, thyrotrophic stimulating hormone (TSH) (0.5 U/100 g body wt twice daily) was given on days 10-13, with uptake measured on day 16. Following TSH treatment, only passive transport for taurocholate was observed in the ileum; uptake rates were consistently higher than those for untreated controls at each study concentration. Thyroidectomy performed at age 14 days with uptake measured at age 21 days did not ablate development of ileal active transport but resulted in a significant reduction (P less than 0.001) in the Vapp (7.39 +/- 1.10 nmol X min-1 X mg dry wt-1) and a significant increase (P less than 0.014) in Km (1.72 +/- 0.53 mM) compared with age-matched controls. Thyroid hormone does not appear to be obligatory for the postnatal development of ileal active taurocholate transport.

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