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American Journal of Physiology. Renal... Jul 2010The fine regulation of Na(+) and K(+) transport takes place in the cortical distal nephron. It is well established that K(+) secretion occurs through apical K(+)...
The fine regulation of Na(+) and K(+) transport takes place in the cortical distal nephron. It is well established that K(+) secretion occurs through apical K(+) channels: the ROMK and the Ca(2+)- and voltage-dependent maxi-K. Previously, we identified the voltage-gated Kv1.3 channel in the inner medulla of the rat kidney (Escobar LI, Martínez-Téllez JC, Salas M, Castilla SA, Carrisoza R, Tapia D, Vázquez M, Bargas J, Bolívar JJ. Am J Physiol Cell Physiol 286: C965-C974, 2004). To examine the role of Kv1.3 in the renal regulation of K(+) homeostasis, we characterized the effect of dietary K(+) on the molecular and functional expression of this channel. We performed real-time-PCR and immunoblot assays in kidneys from rats fed a control (CK; 1.2% wt/wt) or high-K(+) (HK; 10% wt/wt) diet for 5-15 days. Kv1.3 mRNA and protein expression did not change with HK in the whole kidney. However, dietary K(+) loading provoked a change in the cellular distribution of Kv1.3 from the cytoplasm to apical membranes. Immunolocalization of Kv1.3 detected the channel exclusively in the intercalated cells. We investigated whether Kv1.3 mediated K(+) transport in microperfused cortical collecting ducts (CCDs). The HK diet led to an increase in net K(+) transport from 7.4 +/- 1.1 (CK) to 11.4 +/- 1.0 (HK) pmol x min(-1.) mm(-1). Luminal margatoxin, a specific blocker of Kv1.3, decreased net K(+) secretion in HK CCDs to 6.0 +/- 1.6 pmol x min(-1.) mm(-1). Our data provide the first evidence that Kv1.3 channels participate in K(+) secretion and that apical membrane localization of Kv1.3 is enhanced in the intercalated cells by dietary K(+) loading.
Topics: Animals; Blotting, Western; Homeostasis; Hydrogen-Ion Concentration; Immunohistochemistry; Ion Channel Gating; Kidney; Kinetics; Kv1.3 Potassium Channel; Male; Membrane Potentials; Microscopy, Fluorescence; Perfusion; Potassium Channel Blockers; Potassium, Dietary; Protein Transport; RNA, Messenger; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; Scorpion Venoms; Time Factors; Urinalysis
PubMed: 20427469
DOI: 10.1152/ajprenal.00697.2009 -
Endocrinology and Metabolism Clinics of... Sep 1995This article reviews the potential effects of dietary constituents and manipulations on blood pressure. Dietary approaches with documented efficacy are discussed, as are... (Review)
Review
This article reviews the potential effects of dietary constituents and manipulations on blood pressure. Dietary approaches with documented efficacy are discussed, as are the effects of other nutritional factors, which, after study, demonstrate no proven change on blood pressure. The effects of dietary ions (micronutrients) and of individual dietary macronutrients also are reviewed. The article concludes by examining the evidence for effects of weight loss, alcohol restriction, and vegetarian diets and offers for future research.
Topics: Blood Pressure; Calcium, Dietary; Diet, Vegetarian; Dietary Fats; Humans; Hypertension; Potassium, Dietary; Sodium, Dietary; Weight Loss
PubMed: 8575414
DOI: No ID Found -
American Journal of Veterinary Research Apr 2000To assess the effect of dietary potassium citrate supplementation on the urinary pH, relative supersaturation of calcium oxalate and struvite (defined as the activity...
OBJECTIVE
To assess the effect of dietary potassium citrate supplementation on the urinary pH, relative supersaturation of calcium oxalate and struvite (defined as the activity product/solubility product of the substance), and concentrations of magnesium, ammonium, phosphate, citrate, calcium, and oxalate in dogs.
ANIMALS
12 healthy adult dogs.
PROCEDURE
Canned dog food was fed to dogs for 37 days. Dogs were randomly allocated to 3 groups and fed test diets for a period of 8 days. Study periods were separated by 6-day intervals. During each study period the dogs were fed either standard diet solus (control) or standard diet plus 1 of 2 types of potassium citrate supplements (150 mg potassium citrate/kg of body weight/d) twice daily. Urinary pH, volume and specific gravity, relative supersaturation of calcium oxalate and struvite, and concentrations of magnesium, ammonium, phosphate, calcium, oxalate, and citrate were assessed for each treatment.
RESULTS
Mean urine pH was not significantly affected by dietary potassium citrate supplementation, although urine pH did increase by 0.2 pH units with supplementation. Diets containing potassium citrate maintained a higher urine pH for a longer part of the day than control diet. Three Miniature Schnauzers had a significantly lower urinary relative calcium oxalate supersaturation when fed a diet supplemented with potassium citrate, compared with control diet.
CONCLUSIONS AND CLINICAL RELEVANCE
Dietary potassium citrate supplementation has limited effects on urinary variables in most healthy dogs, although supplementation results in maintenance of a higher urine pH later in the day. Consequently, if supplementation is introduced, dogs should be fed twice daily and potassium citrate should be given with both meals or with the evening meal only.
Topics: Animals; Body Weight; Calcium Oxalate; Circadian Rhythm; Dogs; Energy Intake; Female; Hydrogen-Ion Concentration; Magnesium Compounds; Male; Phosphates; Potassium Citrate; Potassium, Dietary; Struvite; Urine
PubMed: 10772109
DOI: 10.2460/ajvr.2000.61.430 -
Journal of Animal Physiology and Animal... Jun 2014Dry cow diets based on grassland forage from intensive production contain high amounts of K and could be responsible for a reduced ability to maintain Ca homoeostasis....
Dry cow diets based on grassland forage from intensive production contain high amounts of K and could be responsible for a reduced ability to maintain Ca homoeostasis. The aim of this study was to determine whether a moderate anionic salt supplementation to a forage-based pre-calving diet with varying native K content affects the mineral and acid-base status in transition cows. Twenty-four dry and pregnant Holstein cows, without antecedent episodes of clinical hypocalcemia, were assigned to two diets during the last 4 weeks before estimated calving date. Twelve cows were fed a hay-based diet low in K (18 g K/kg DM), and 12, a hay-based diet high in K (35 g K/kg DM). Within each diet, six cows received anionic salts during the last 2 weeks before the estimated calving day. After calving, all cows received the high K diet ad libitum. Blood samples were taken daily from day 11 pre-partum to day 5 post-partum. Urine samples were taken on days 7 and 2 pre-partum and on day 2 post-partum. The anionic salt did not alter feed intake during the pre-partum period. Serum Ca was not influenced by the dietary treatments. Feeding pre-partum diets with low K concentrations induced a reduced metabolic alkalotic charge, as indicated by reduced pre-partum urinary base-acid quotient. Transition cows fed the low K diet including anionic salts induced a mild metabolic acidosis before calving, as indicated by higher urinary Ca, lower urinary pH and net acid-base excretion. Although serum Ca during the post-partum period was not affected by dietary treatment, feeding a low K diet moderately supplemented with anionic salts to reach a dietary cation-anion difference close to zero permitted to obtain a metabolic response in periparturient cows without altering the dry matter intake.
Topics: Acid-Base Equilibrium; Animal Feed; Animal Nutritional Physiological Phenomena; Animals; Anions; Calcium; Cattle; Diet; Dietary Supplements; Female; Homeostasis; Parturition; Peripartum Period; Potassium, Dietary; Pregnancy; Time Factors
PubMed: 23796109
DOI: 10.1111/jpn.12093 -
Journal of Animal Science Jun 1991The apparent retention and excretion of cations and anions were evaluated in 20 growing pigs to study the mechanisms by which an interaction between dietary K and Cl...
The apparent retention and excretion of cations and anions were evaluated in 20 growing pigs to study the mechanisms by which an interaction between dietary K and Cl levels affected growth. All pigs maintained a positive retention of K+ and Cl- regardless of the dietary levels. The K x Cl interaction observed in growth studies previously but not in this study could not be explained by a simple interaction of one ion on the retention of the other. When pooled across dietary Cl levels, an increase in dietary K levels from .10 to .60% resulted in a calculated increase in daily K+ intake of 4.86 meq/kg of BW. Sixty percent (2.99 meq) of the increased K+ intake was excreted in the urine and counterbalanced by a decrease in urine NH4+ (3.06 meq). This decrease in NH4+ excretion could account for essentially all of the increase in N retention (3.51 mmol) observed when dietary K levels were increased from .10 to .60%. Thirty-three percent of the increased K+ intake (1.62 meq) was retained, but the counter ion could not be determined. Retention of Cl- was not changed as dietary K levels were changed. When dietary Cl levels were increased from .03 to .57%, 69% (4.06 meq) of the calculated difference in Cl- intake (5.90 meq) was excreted in the urine, which must have been counterbalanced by a decrease in undetermined organic anions (1.77 meq) and HPO4 = (1.50 meq) excretion, with a tendency for an increased NH4+ (.82 meq) excretion. The counter ions required to balance the increased Cl- retention (1.82 meq) as dietary Cl levels were increased from .03 to .57% could not be identified. Shifts in the retention and urinary excretion of Ca++, Na+, HCO3-, and SO4= did not seem to be quantitatively important in identifying the mechanisms by which dietary K and Cl levels alter growth. Based on these results, we conclude that alterations in growth caused by changes in dietary K and possibly Cl levels are mediated via mechanisms involving renal NH4+ metabolism.
Topics: Ammonia; Animals; Anions; Calcium; Cations; Chlorides; Diet; Digestion; Male; Potassium; Random Allocation; Swine; Urination; Water-Electrolyte Balance
PubMed: 1885366
DOI: 10.2527/1991.6962504x -
Proceedings of the National Academy of... Jul 2010Tissue kallikrein (TK) is a serine protease synthetized in renal tubular cells located upstream from the collecting duct where renal potassium balance is regulated....
Tissue kallikrein (TK) is a serine protease synthetized in renal tubular cells located upstream from the collecting duct where renal potassium balance is regulated. Because secretion of TK is promoted by K+ intake, we hypothesized that this enzyme might regulate plasma K+ concentration ([K+]). We showed in wild-type mice that renal K+ and TK excretion increase in parallel after a single meal, representing an acute K+ load, whereas aldosterone secretion is not modified. Using aldosterone synthase-deficient mice, we confirmed that the control of TK secretion is aldosterone-independent. Mice with TK gene disruption (TK-/-) were used to assess the impact of the enzyme on plasma [K+]. A single large feeding did not lead to any significant change in plasma [K+] in TK+/+, whereas TK-/- mice became hyperkalemic. We next examined the impact of TK disruption on K+ transport in isolated cortical collecting ducts (CCDs) microperfused in vitro. We found that CCDs isolated from TK-/- mice exhibit net transepithelial K+ absorption because of abnormal activation of the colonic H+,K+-ATPase in the intercalated cells. Finally, in CCDs isolated from TK-/- mice and microperfused in vitro, the addition of TK to the perfusate but not to the peritubular bath caused a 70% inhibition of H+,K+-ATPase activity. In conclusion, we have identified the serine protease TK as a unique kalliuretic factor that protects against hyperkalemia after a dietary K+ load.
Topics: Adaptation, Physiological; Aldosterone; Animals; Biological Transport; Cytochrome P-450 CYP11B2; H(+)-K(+)-Exchanging ATPase; Hydrogen-Ion Concentration; In Vitro Techniques; Kidney; Kidney Tubules, Collecting; Mice; Mice, Knockout; Potassium; Potassium, Dietary; Reverse Transcriptase Polymerase Chain Reaction; Sodium; Tissue Kallikreins
PubMed: 20624970
DOI: 10.1073/pnas.0913070107 -
Internal Medicine (Tokyo, Japan) Aug 1992The pathogenesis of renal potassium wasting and hypokalemia in classic renal tubular acidosis (type 1 RTA) remains uncertain. The prevailing theory is that K(+)-Na+...
The pathogenesis of renal potassium wasting and hypokalemia in classic renal tubular acidosis (type 1 RTA) remains uncertain. The prevailing theory is that K(+)-Na+ exchange is stimulated due to an inability of the distal tubule to establish a normal steep lumen-peritubular H+ gradient. We encountered a 42-year-old woman with type 1 RTA associated with Sjögren's syndrome, in whom renal potassium wasting and hypokalemia persisted despite sustained correction of systemic acidosis with alkali therapy and increased intake of potassium. In addition, plasma renin activity was markedly increased and the serum aldosterone level was upper-normal despite the hypokalemia. Increased intake of sodium resulted in suppression on the serum aldosterone and correction of renal potassium wasting and hypokalemia. This case shows that secondary hyperaldosteronism, possibly due to an impairment of sodium conservation in the distal tubule, may contribute to the loss of potassium from the distal tubule even after the correction of acidosis.
Topics: Acidosis, Renal Tubular; Adult; Aldosterone; Ammonium Chloride; Bicarbonates; Blood Gas Analysis; Female; Humans; Hydrogen-Ion Concentration; Hyperaldosteronism; Hypokalemia; Kidney; Potassium; Potassium, Dietary; Sjogren's Syndrome; Sodium; Sodium Bicarbonate; Sodium, Dietary; Urine; Water-Electrolyte Balance
PubMed: 1335804
DOI: 10.2169/internalmedicine.31.1047 -
The American Journal of Physiology Jun 1998Potassium reduces blood pressure in populations at high risk of developing hypertension, which suggests that potassium depletion may increase vascular resistance. This...
Potassium reduces blood pressure in populations at high risk of developing hypertension, which suggests that potassium depletion may increase vascular resistance. This study was designed to examine the effect of potassium depletion on the L-arginine-nitric oxide pathway in arterial tissues. New Zealand White rabbits were fed either a control diet, containing a normal amount of potassium, or a low-potassium diet for 1-3 wk. As expected, the low-potassium diet resulted in reduced serum and urinary potassium levels. Carotid arteries were excised, and their contractile and relaxant responses were determined in vitro. Carotid arterial ring contractile response to norepinephrine was enhanced, and relaxation in response to the endothelium-dependent vasodilators acetylcholine and calcium ionophore A-23187 was attenuated, in rabbits fed low-potassium diet (all P < 0.01 compared with responses in rabbits fed control diet). The vasomotor responses were similarly altered in rabbits fed low-potassium diet for 1 or 3 wk. Both the enhanced contraction and attenuated relaxation were abolished by treatment of arterial rings with superoxide dismutase but not by treatment with L-arginine or indomethacin. Carotid artery rings from rabbits fed the low-potassium diet showed approximately 100% greater superoxide anion formation than those from rabbits fed control diet (P < 0.01), whereas plasma and urinary nitrite levels were similar in both groups of rabbits. These observations indicate that low-potassium diet enhances the sensitivity of the carotid artery to vasoconstrictor stimuli and reduces the sensitivity to endothelium-dependent stimuli. Attenuation of endothelium-dependent relaxation appears to be secondary to increased free radical generation, which may degrade nitric oxide. Altered vasoreactivity may underlie the genesis of hypertension in populations consuming diets low in potassium.
Topics: Acetylcholine; Animals; Arginine; Calcimycin; Carotid Arteries; Indomethacin; Nitric Oxide; Norepinephrine; Potassium; Potassium, Dietary; Rabbits; Superoxide Dismutase; Superoxides; Vasoconstriction; Vasoconstrictor Agents; Vasodilation; Vasodilator Agents
PubMed: 9841522
DOI: 10.1152/ajpheart.1998.274.6.H1955 -
The Journal of Physiology Apr 1952
Topics: Animals; Axons; Ions; Loligo; Potassium; Sodium; Sodium, Dietary
PubMed: 14946713
DOI: 10.1113/jphysiol.1952.sp004717 -
Metabolism: Clinical and Experimental Feb 1964
Topics: Blood Chemical Analysis; Chlorides; Chromatography; Electrolytes; Ion Exchange; Ion Exchange Resins; Potassium; Potassium Isotopes; Research; Sodium; Sodium Isotopes; Sodium, Dietary; Urine
PubMed: 14127086
DOI: 10.1016/0026-0495(64)90125-8