Aldosterone and thyroid hormone interaction on the sodium and potassium transport pathways of rat colonic epithelium

1990 ◽  
Vol 124 (1) ◽  
pp. 47-52 ◽  
Author(s):  
C. J. Edmonds ◽  
C. L. Willis
Keyword(s):  
Electrical Potential ◽  
Dry Weight ◽  
Potassium Transport ◽  
Plasma Sodium ◽  
Electrical Potential Difference ◽  
Stimulant Effect ◽  
Potassium Adaptation ◽  
Short Period ◽  
Potassium Secretion ◽  
Sodium And Potassium

ABSTRACT The effect of hypothyroidism on potassium adaptation (shown by increased potassium secretion in response to potassium loading) and on the action of aldosterone on potassium secretion and sodium fluxes was examined in the rat distal colon. Potassium adaptation, particularly the response to an acute potassium load, was impaired by hypothyroidism which also considerably reduced the rise of transepithelial electrical potential difference (p.d.) of total and transcellular (active) lumen-to-plasma sodium fluxes and of potassium secretion normally produced by aldosterone. These changes were, in part, corrected by a short period (3 days) of tri-iodothyronine replacement. Moreover in aldosterone-treated hypothyroid rats, amiloride in the lumen was considerably less effective in reducing the p.d. and sodium fluxes than in aldosterone-treated normal rats. The intracellular sodium transport pool was greater in the hypothyroid than in the normal rats (5·0± 1·1 (s.e.m.) nmol/mg dry weight compared with 2·9 ± 0·2 nmol/mg dry weight; P<0·02). Aldosterone increased the pool in the normal but not in the hypothyroid rats while amiloride had little effect on the pool in the aldosterone-treated hypothyroid rats but almost abolished it in aldosterone-treated normal rats. Aldosterone plays a major part in the adaptation of colonic sodium and potassium transport to sodium depletion or potassium excess; these adaptations were much impaired in hypothyroid animals. The present results are consistent with a deficiency in aldosterone induction of potassium- and amiloride-sensitive sodium pathways in the apical membrane of colonic epithelial cells in hypothyroid rats, a deficiency which limits the stimulant effect of aldosterone on sodium and potassium transport. Journal of Endocrinology (1990) 124, 47–52

Control of potassium transport by turtle colon: role of membrane potential

1984 ◽  
Vol 247 (1) ◽  
pp. C26-C32 ◽  
Author(s):  
D. R. Halm ◽  
D. C. Dawson
Keyword(s):  
Electrical Potential ◽  
Potassium Transport ◽  
Sodium Absorption ◽  
Electrical Potential Difference ◽  
Sodium Potassium ◽  
Pump Rate ◽  
Potassium Secretion ◽  
Sodium Potassium Pump

To more clearly define the role of the transepithelial electrical potential difference (V m----s), potassium permeability, and sodium-potassium pump rate in transcellular potassium transport by isolated turtle colon, we measured transmural potassium fluxes under open-circuit conditions in the presence and absence of putative blockers of potassium transport: amiloride and barium. The results were consistent with the notion that V m----s is a major determinant of cellular potassium secretion, whereas active potassium absorption is insensitive to changes in V m----s. These observations suggest that “coupling” between colonic sodium absorption and potassium secretion in vivo could be due primarily to the effect of the lumen negative V m----s on transcellular secretory potassium flow. Amiloride-induced inhibition of potassium secretion appeared to be due to the reductions in V m----s and sodium-potassium pump rate that accompanied the inhibition of active sodium absorption.

Effects of flow rate and potassium intake on distal tubular potassium transfer

1975 ◽  
Vol 228 (4) ◽  
pp. 1249-1261 ◽  
Author(s):  
RN Khuri ◽  
WN Strieder ◽  
G Giebisch
Keyword(s):  
Flow Rate ◽  
Electrical Potential ◽  
Isotonic Saline ◽  
Distal Tubule ◽  
Sodium Reabsorption ◽  
Electrical Potential Difference ◽  
High Potassium ◽  
Flow Rates ◽  
Potassium Intake ◽  
Potassium Secretion

Potassium transport was studied across proximal and distal tubular epithelium in rats on a normal, low- and high-potassium intake during progressive loading with isotonic saline (150 mM) or a moderately hypersomotic urea (200 mM) sodium chloride (100 mM) solution. Free-flow micropuncture and recollection techniques were used during the development of diruesis and tubular fluid (TF) analyzed for inulin-14C, potassium (K) and sodium (Na). Tubular puncture sites were localized by neoprene filling and microdissection. During the large increase in tubular flow rates (10 times): 1) fractional potassium reabsorption fell along the proximal tubule, 2) TFk along the distal tubule remained constant and independent of flow rate in control and high-k rats; thus, net potassium secretion increased in proportion to and was limited by flow rate. 3) In low-K rats TF k fell; with increasing flow rates distal K secretion was not effectively stimulated. 4) Distal tubular sodium reabsorption increased in all animals with flow rate, but tubular Na-K exchange ratios varied greatly. It is suggested that whenever sodium delivery stimulates distal tubular potassium secretion it does so by 1) increasing volume distal tubular potasssium secretion and by 2) augmenting the transepithelial electrical potential difference (lumen negative).

Bidirectional sodium fluxes across the placenta of conscious sheep

1978 ◽  
Vol 235 (6) ◽  
pp. F536-F541
Author(s):  
A. P. Weedon ◽  
T. E. Stacey ◽  
R. H. Ward ◽  
R. D. Boyd
Keyword(s):  
Electrical Potential ◽  
Flux Ratio ◽  
Sodium Concentration ◽  
Plasma Sodium ◽  
Electrical Potential Difference ◽  
Single Experiment ◽  
Blood Flows ◽  
Fetal Plasma ◽  
Pregnant Sheep ◽  
Intravascular Catheters

Conscious pregnant sheep in the last 3 wk of gestation were studied 1––3 days after surgery. Fetal plasma sodium concentration was significantly lower than maternal. A mean electrical potential difference (PD) of 34 +/- 4 (SE) mV (n = 24) was recorded between maternal and fetal intravascular catheters, the mother being positive with reference to fetus. Unidirectional fetomaternal (Jf leads to m) and maternofetal (Jm leads to f) sodium fluxes were determined by application of Fick's principle to uterine and umbilical circulations following injection of 22NaCl or 24NaCl to fetus or mother, respectively. Blood flows were measured by an antipyrine technique. Jm leads to f = 0.142 +/- 0.029 mmol/min (n = 10); Jf leads to m =0.137 +/- 0.015 mmol/min (n = 21). Jm leads to f increased as a linear function of calculated fetal weight. In seven sheep both Jm leads to f and Jf leads to m were measured in a single experiment. The measured ratio Jm leads to f/Jf leads to m was significantly different from the ratio predicted using Ussing's flux ratio equation. There is probably a transplacental sodium pump active in the direction fetus to mother.

scholarly journals Electrical potential difference and absorption of water, sodium, and potassium by the terminal ileum of ileostomy patients

Gut ◽  
1974 ◽  
Vol 15 (12) ◽  
pp. 977-981 ◽  
Author(s):  
J. P. P. De Moraes-Filho ◽  
C. Salas-Coll ◽  
L. Blendis ◽  
C. J. Edmonds
Keyword(s):  
Terminal Ileum ◽  
Electrical Potential ◽  
Potential Difference ◽  
Electrical Potential Difference ◽  
Sodium And Potassium

Sodium and Potassium Transport Rates in Normal Human Leucocytes in Hypo-Osmolal Extracellular Fluid

1974 ◽  
Vol 46 (5) ◽  
pp. 613-617 ◽  
Author(s):  
P. J. Hilton ◽  
J. Patrick
Keyword(s):  
Rate Constants ◽  
Extracellular Fluid ◽  
Dry Weight ◽  
Potassium Transport ◽  
Sodium Influx ◽  
Potassium Efflux ◽  
Normal Human ◽  
Potassium Influx ◽  
Sodium And Potassium

1. Sodium and potassium transport rates were studied in normal human leucocytes exposed to iso-osmolal and hypo-osmolal extracellular fluid. 2. Hypo-osmolality of the extracellular fluid led to an increase in sodium influx and a decrease in potassium influx expressed as mmol h−1 kg−1 cell dry weight. The fall in potassium influx was smaller than the rise in sodium influx and was confined to the ouabain-insensitive portion of the flux. 3. The rate constants for sodium and potassium efflux did not differ significantly between the iso-osmolal and hypo-osmolal media.

Effects of changes in electrical potential difference on tubular potassium transport

1980 ◽  
Vol 238 (3) ◽  
pp. F235-F246 ◽  
Author(s):  
E. Garcia-Filho ◽  
G. Malnic ◽  
G. Giebisch
Keyword(s):  
Potassium Concentration ◽  
Electrical Potential ◽  
Potential Drop ◽  
Plasma Potassium ◽  
Potential Difference ◽  
Electrical Potential Difference ◽  
High Potassium ◽  
Transepithelial Potential ◽  
Wide Range ◽  
Potassium Secretion

To assess directly the role of the transepithelial potential difference (PD) on potassium concentration differences across distal tubular epithelium, continuous and stationary microperfusion experiments were done in tubules voltage-clamped over a wide range of lumen-negative potentials. Potassium was measured either chemically or in situ by potassium-sensitive microelectrodes. Distal cell PD measurements show that most of the potential drop induced by luminal current injection occurred across the luminal cell membrane. Experiments were done in rats either on a control or on a high potassium diet and after amiloride administration. Luminal potassium was highly sensitive to imposed electrical potential changes, attainment of a new steady-state intraluminal potassium concentration was rapid (less than 1 s), and higher luminal potassium concentrations were observed in animals in which potassium secretion had been stimulated. Similar slopes of tubular fluid-to-plasma potassium ratios versus transepithelial potential differences were observed in all experiments. All slopes intersected, at zero PD, at a luminal tubular fluid-to-plasma concentration ratio in excess of unity, indicating the presence of an active component of potassium secretion.

scholarly journals Renal potassium transport: the pioneering studies of Gerhard Giebisch

2010 ◽  
Vol 298 (2) ◽  
pp. F233-F234 ◽  
Author(s):  
Bruce A. Stanton
Keyword(s):  
Rat Kidney ◽  
Distal Tubule ◽  
Potassium Transport ◽  
Historical Significance ◽  
Potassium Adaptation ◽  
Micropuncture Study ◽  
On Line ◽  
Potassium Secretion ◽  
Distal Tubules ◽  
Renal Potassium Excretion

This essay looks at the historical significance of six APS Classic Papers that are freely available on line: Malnic G, Klose RM, Giebisch G. Micropuncture study of renal potassium excretion in the rat. Am J Physiol 206: 674–686, 1964 ( http://ajplegacy.physiology.org/cgi/reprint/206/4/674 ). Malnic G, Klose RM, Giebisch G. Micropuncture study of distal tubular potassium and sodium transport in rat nephron. Am J Physiol 211: 529–547, 1966 ( http://ajplegacy.physiology.org/cgi/reprint/211/3/529 ). Malnic G, Klose RM, Giebisch G. Microperfusion study of distal tubular potassium and sodium transfer in rat kidney. Am J Physiol 211: 548–559, 1966 ( http://ajplegacy.physiology.org/cgi/reprint/211/3/548 ). Duarte CG, Chomety F, Giebisch G. Effect of amiloride, ouabain, and furosemide on distal tubular function in the rat. Am J Physiol 221: 632–640, 1971 ( http://ajplegacy.physiology.org/cgi/reprint/221/2/632 ). Malnic G, De Mello Aires M, Giebisch G. Potassium transport across renal distal tubules during acid-base disturbances. Am J Physiol 221: 1192–1208, 1971 ( http://ajplegacy.physiology.org/cgi/reprint/221/4/1192 ). Wright FS, Strieder N, Fowler NB, Giebisch G. Potassium secretion by distal tubule after potassium adaptation. Am J Physiol 221: 437–448, 1971 ( http://ajplegacy.physiology.org/cgi/reprint/221/2/437 ).

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