Sodium Fate after Sodium Bicarbonate Infusion: Influence of Altered Acid-Base Status.

BACKGROUND: We have previously investigated the fate of administered bicarbonate infused as a hypertonic solution in animals with each of the 4 chronic acid-base disorders. Those studies did not address the fate of sodium, the coadministered cation. METHODS: We examined baseline total body water (TBW), Na+ space, HCO3- space, and urinary sodium and bicarbonate excretion after acute hypertonic NaHCO3 infusion (1-N solution, 5 mmol/kg body weight) in dogs with each of the 4 chronic acid-base disorders. Observations were made at 30, 60, and 90 min postinfusion. Retained sodium that remains osmotically active distributes in an apparent space that approximates TBW. Na+ space that exceeds TBW uncovers nonosmotic sodium storage. RESULTS: Na+ space approximated TBW at all times in normal and hyperbicarbonatemic animals (metabolic alkalosis and respiratory acidosis), but exceeded TBW by ~30% in hypobicarbonatemic animals (metabolic acidosis and respiratory alkalosis). Such osmotic inactivation was detected at 30 min and remained stable. The pooled data revealed that Na+ space corrected for TBW was independent of the initial blood pH but correlated with initial extracellular bicarbonate concentration (y = -0.01x + 1.4, p= 0.002). The fate of administered sodium and bicarbonate (internal distribution and urinary excretion) was closely linked. CONCLUSIONS: This study demonstrates that hypobicarbonatemic animals have a Na+ space that exceeds TBW after an acute infusion of hypertonic NaHCO3 indicating osmotic inactivation of a fraction of retained sodium. In addition to an expanded Na+ space, these animals have a larger HCO3- space compared with hyperbicarbonatemic animals. Both phenomena appear to reflect the wider range of titration of nonbicarbonate buffers (Δ pH) occurring during NaHCO3- loading whenever initial [HCO3-]e is low. The data indicate that the fate of administered bicarbonate drives the internal distribution and the external disposal of sodium, the co-administered cation, and is responsible for the early, but non-progressive, osmotic inactivation of a fraction of the retained sodium.

Aptamer biosensor for label-free impedance spectroscopy detection of potassium ion based on DNA G-quadruplex conformation.

Herein, a label-free and highly sensitive electrochemical impedance spectroscopy (EIS) aptasensor for the detection of potassium ion (K⁺) was developed based on a conformational change in which a K⁺-stabilized single stranded DNA (ssDNA) with G-rich sequence was used as the recognition element. In the measurement of K⁺ ions, the change in interfacial electron transfer resistance (R(ct)) of the sensor using a redox couple of [Fe(CN)6]³â»/4⁻ as the probe was monitored. In the presence of K⁺, the G-rich DNA folded into the G-quadruplex structure, and then K⁺ can bind to the G-quadruplex structure, leading to an increase in the R(ct). The Rct increased with K⁺ concentration, and the plot of R(ct) against the logarithm of K⁺ concentration is linear over the range from 0.1 nM to 1 mM with a detection limit of 0.1 nM. Other metal ions, such as Ca²âº, Mg²âº, Na⁺, Li⁺, Al³âº, Zn²âº, Cu²âº, and Ni²âº caused no notable interference on the detection of K⁺. The scheme reported herein is applicable to the detection of other kinds of G-rich aptamer-binding chemicals and biomolecules.

Analysis of renal stones by capillary isotachophoresis.

An analytical method for the determination of the composition of renal stones by capillary isotachophoresis with conductometric detection was developed. Using different leading/terminating electrolyte systems, the qualitative and quantitative analysis of organic compounds (urate, xanthate, oxalate) and inorganic ions (phosphate, Ca(2+), Mg(2+), Na(+), NH(4)(+)) species commonly present in mixed renal stones in three separate steps can be carried out with limits of detection about 10 µmol/L. The developed method was validated by the analysis of real samples and can be used for urinary calculi classification. In addition, it was verified that this method can also be employed for the determination of the above mentioned analytes in some other samples (bones, teeth) concerning apatite biominerals (fluoro-, carbonate-, chloro-apatite).

[Physiological analysis of various types of osmotic diuresis].

Efficacy of drugs reduced proximal reabsorption was compared in experiments with female Wistar rats. Urine flow rate for the 1st h of experiment was enhanced after polyethylene glycol-400 (PEG) and 6% Na2SO4 infusion by over 30-fold, exenatide--40-fold, glycerol--11-fold as compared with the control. The maximal values of Na+ excretion were observed during Na2SO4 and exenatide administration (280 +/- 31 micromol/h vs. 3.2 +/- 0.6 Imol/h/100 g bw). The highest K+ excretion was revealed in experiments with glycerol administration (41 +/- 5 micromol/h vs. 7 +/- 2 micromol/h/100 g bw), Mg2+ --after exenatide injection (5.3 +/- 1.3 micromol/h vs. 0.16 +/- 0.03 micromol/ h/100 g bw). Diuretic effects were additive after combined administration of maximal doses of exenatide and PEG which suggests a different mechanism of action of solutes filtrated (PEG) to the proximal nephron segment and generated due to Na+/HW-exchange inhibition (exenatide). Osmotic diuretics differ by potency, mechanism of diuretic action and selectivity of ion excretion).

Analysis of BP response and Ca2+ metabolism using the saturation kinetics model.

The provision of supplemental dietary calcium (dCa) lowers blood pressure (BP) in the spontaneously hypertensive rat (SHR). Whether calcium's antihypertensive effects can be expressed in the presence of potentially hypertensinogenic nutrients is not known. Furthermore, the amount of dCa required to attenuate hypertension in the SHR remains undetermined. Along with establishing the effects of dCa on BP under conditions of a high Na+ intake, we sought to define the lowest dose of dCa associated with the greatest attenuation in arterial pressure in the young SHR. Thirty-five 6-wk-old SHR were fed one of five diets containing either 0.1, 0.25, 0.5, 1.0, or 2.0% dCa. All diets contained 1.0% Na+. The rates of change (delta) in body weight, BP, and serum ionized calcium were determined between 6 and 20 wk of age. Bone density (BD) was measured only at 20 wk of age. The data were analyzed using the saturation kinetics model. Results indicate that the half-maximal dose (K50) of dCa needed to lower pressure is 0.67 +/- 0.18%, which is higher than the K50 for weight (0.23 +/- 0.18) and BD (0.36 +/- 0.22). It is concluded that supplemental dCa lowers BP despite a high Na+ intake. Furthermore, a dose of approximately 1.5 dCa is sufficient to attenuate the rate of hypertension in the young growing SHR.